In ImageMagick 7.0.8-36 Q16, there is a memory leak in the function SVGKeyValuePairs of coders/svg.c, which allows an attacker to cause a denial of service via a crafted image file.
### Prerequisites

- [Y] I have written a descriptive issue title
- [Y] I have verified that I am using the latest version of ImageMagick
- [Y] I have searched [open](https://github.com/ImageMagick/ImageMagick/issues) and [closed](https://github.com/ImageMagick/ImageMagick/issues?q=is%3Aissue+is%3Aclosed) issues to ensure it has not already been reported

### Description
<!-- A description of the bug or feature -->
There is a memory leak vulnerability in function SVGKeyValuePairs of coders/svg.c.

### Steps to Reproduce
<!-- List of steps, sample code, failing test or link to a project that reproduces the behavior.
     Make sure you place a stack trace inside a code (```) block to avoid linking unrelated issues -->
[poc](https://drive.google.com/open?id=178I9vAWVNgp4Fwn9PZxaVZuLHaJyTPC-)
magick convert $poc /dev/null
`=================================================================`
`==8783==ERROR: LeakSanitizer: detected memory leaks`

`Direct leak of 144 byte(s) in 1 object(s) allocated from:`
`    #0 0x7f1f6d7c1961 in realloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x98961)`
`    #1 0x441b30 in ResizeMagickMemory MagickCore/memory.c:1302`
`    #2 0x441bb4 in ResizeQuantumMemory MagickCore/memory.c:1366`
`    #3 0x6d3c1c in SVGKeyValuePairs coders/svg.c:752`
`    #4 0x6df888 in SVGEndElement coders/svg.c:2811`
`    #5 0x7f1f6a0ae91c  (/usr/lib/x86_64-linux-gnu/libxml2.so.2+0x4c91c)`

`Direct leak of 80 byte(s) in 1 object(s) allocated from:`
`    #0 0x7f1f6d7c1602 in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x98602)`
`    #1 0x440828 in AcquireMagickMemory MagickCore/memory.c:478`
`    #2 0x44087c in AcquireQuantumMemory MagickCore/memory.c:551`
`    #3 0x6d3b13 in SVGKeyValuePairs coders/svg.c:733`
`    #4 0x6df888 in SVGEndElement coders/svg.c:2811`
`    #5 0x7f1f6a0ae91c  (/usr/lib/x86_64-linux-gnu/libxml2.so.2+0x4c91c)`

`Indirect leak of 71185 byte(s) in 17 object(s) allocated from:`
`    #0 0x7f1f6d7c1602 in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x98602)`
`    #1 0x440828 in AcquireMagickMemory MagickCore/memory.c:478`
`    #2 0x44087c in AcquireQuantumMemory MagickCore/memory.c:551`
`    #3 0x4c22c5 in AcquireString MagickCore/string.c:142`
`    #4 0x6d3cad in SVGKeyValuePairs coders/svg.c:760`
`    #5 0x6df888 in SVGEndElement coders/svg.c:2811`
`    #6 0x7f1f6a0ae91c  (/usr/lib/x86_64-linux-gnu/libxml2.so.2+0x4c91c)`

`Indirect leak of 8194 byte(s) in 2 object(s) allocated from:`
`    #0 0x7f1f6d7c1602 in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x98602)`
`    #1 0x440828 in AcquireMagickMemory MagickCore/memory.c:478`
`    #2 0x44087c in AcquireQuantumMemory MagickCore/memory.c:551`
`    #3 0x4c22c5 in AcquireString MagickCore/string.c:142`
`    #4 0x6d3dd3 in SVGKeyValuePairs coders/svg.c:766`
`    #5 0x6df888 in SVGEndElement coders/svg.c:2811`
`    #6 0x7f1f6a0ae91c  (/usr/lib/x86_64-linux-gnu/libxml2.so.2+0x4c91c)`

`SUMMARY: AddressSanitizer: 79603 byte(s) leaked in 21 allocation(s).`
### System Configuration
<!-- Tell us about the environment where you are experiencing the bug -->

- ImageMagick version:
Version: ImageMagick 7.0.8-36 Q16 x86_64 2019-03-28 https://imagemagick.org
Copyright: ? 1999-2019 ImageMagick Studio LLC
License: https://imagemagick.org/script/license.php
Features: Cipher DPC HDRI OpenMP 
Delegates (built-in): bzlib djvu fftw fontconfig freetype jbig jng jpeg lcms lqr lzma openexr pangocairo png tiff wmf x xml zlib
- Environment (Operating system, version and so on):
Distributor ID:	Ubuntu
Description:	Ubuntu 16.04.2 LTS
Release:	16.04
Codename:	xenial
- Additional information:

<!-- Thanks for reporting the issue to ImageMagick! -->

memory leak in SVGKeyValuePairs of coders/svg.c
This is a GitHub Issue
repo:ImageMagick
owner:ImageMagick
Title : memory leak in SVGKeyValuePairs of coders/svg.c
Issue date:

--- start body ---
### Prerequisites

- [Y] I have written a descriptive issue title
- [Y] I have verified that I am using the latest version of ImageMagick
- [Y] I have searched [open](https://github.com/ImageMagick/ImageMagick/issues) and [closed](https://github.com/ImageMagick/ImageMagick/issues?q=is%3Aissue+is%3Aclosed) issues to ensure it has not already been reported

### Description
<!-- A description of the bug or feature -->
There is a memory leak vulnerability in function SVGKeyValuePairs of coders/svg.c.

### Steps to Reproduce
<!-- List of steps, sample code, failing test or link to a project that reproduces the behavior.
     Make sure you place a stack trace inside a code (```) block to avoid linking unrelated issues -->
[poc](https://drive.google.com/open?id=178I9vAWVNgp4Fwn9PZxaVZuLHaJyTPC-)
magick convert $poc /dev/null
`=================================================================`
`==8783==ERROR: LeakSanitizer: detected memory leaks`

`Direct leak of 144 byte(s) in 1 object(s) allocated from:`
`    #0 0x7f1f6d7c1961 in realloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x98961)`
`    #1 0x441b30 in ResizeMagickMemory MagickCore/memory.c:1302`
`    #2 0x441bb4 in ResizeQuantumMemory MagickCore/memory.c:1366`
`    #3 0x6d3c1c in SVGKeyValuePairs coders/svg.c:752`
`    #4 0x6df888 in SVGEndElement coders/svg.c:2811`
`    #5 0x7f1f6a0ae91c  (/usr/lib/x86_64-linux-gnu/libxml2.so.2+0x4c91c)`

`Direct leak of 80 byte(s) in 1 object(s) allocated from:`
`    #0 0x7f1f6d7c1602 in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x98602)`
`    #1 0x440828 in AcquireMagickMemory MagickCore/memory.c:478`
`    #2 0x44087c in AcquireQuantumMemory MagickCore/memory.c:551`
`    #3 0x6d3b13 in SVGKeyValuePairs coders/svg.c:733`
`    #4 0x6df888 in SVGEndElement coders/svg.c:2811`
`    #5 0x7f1f6a0ae91c  (/usr/lib/x86_64-linux-gnu/libxml2.so.2+0x4c91c)`

`Indirect leak of 71185 byte(s) in 17 object(s) allocated from:`
`    #0 0x7f1f6d7c1602 in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x98602)`
`    #1 0x440828 in AcquireMagickMemory MagickCore/memory.c:478`
`    #2 0x44087c in AcquireQuantumMemory MagickCore/memory.c:551`
`    #3 0x4c22c5 in AcquireString MagickCore/string.c:142`
`    #4 0x6d3cad in SVGKeyValuePairs coders/svg.c:760`
`    #5 0x6df888 in SVGEndElement coders/svg.c:2811`
`    #6 0x7f1f6a0ae91c  (/usr/lib/x86_64-linux-gnu/libxml2.so.2+0x4c91c)`

`Indirect leak of 8194 byte(s) in 2 object(s) allocated from:`
`    #0 0x7f1f6d7c1602 in malloc (/usr/lib/x86_64-linux-gnu/libasan.so.2+0x98602)`
`    #1 0x440828 in AcquireMagickMemory MagickCore/memory.c:478`
`    #2 0x44087c in AcquireQuantumMemory MagickCore/memory.c:551`
`    #3 0x4c22c5 in AcquireString MagickCore/string.c:142`
`    #4 0x6d3dd3 in SVGKeyValuePairs coders/svg.c:766`
`    #5 0x6df888 in SVGEndElement coders/svg.c:2811`
`    #6 0x7f1f6a0ae91c  (/usr/lib/x86_64-linux-gnu/libxml2.so.2+0x4c91c)`

`SUMMARY: AddressSanitizer: 79603 byte(s) leaked in 21 allocation(s).`
### System Configuration
<!-- Tell us about the environment where you are experiencing the bug -->

- ImageMagick version:
Version: ImageMagick 7.0.8-36 Q16 x86_64 2019-03-28 https://imagemagick.org
Copyright: ? 1999-2019 ImageMagick Studio LLC
License: https://imagemagick.org/script/license.php
Features: Cipher DPC HDRI OpenMP 
Delegates (built-in): bzlib djvu fftw fontconfig freetype jbig jng jpeg lcms lqr lzma openexr pangocairo png tiff wmf x xml zlib
- Environment (Operating system, version and so on):
Distributor ID:	Ubuntu
Description:	Ubuntu 16.04.2 LTS
Release:	16.04
Codename:	xenial
- Additional information:

<!-- Thanks for reporting the issue to ImageMagick! -->

--- end body ---
