There is an Assertion `int decode_preR13_entities(BITCODE_RL, BITCODE_RL, unsigned int, BITCODE_RL, BITCODE_RL, Bit_Chain *, Dwg_Data *' failed at dwg2dxf: decode.c:5801 in libredwg v0.12.4.4608.
### system info
Ubuntu x86_64, clang 6.0, dwg2dxf([0.12.4.4608](https://github.com/LibreDWG/libredwg/releases/tag/0.12.4.4608))

### Command line
./programs/dwg2dxf -b -m @@ -o /dev/null

###  output
dwg2dxf: decode.c:5801: int decode_preR13_entities(BITCODE_RL, BITCODE_RL, unsigned int, BITCODE_RL, BITCODE_RL, Bit_Chain *, Dwg_Data *): Assertion `!dat->bit' failed.
Aborted

### poc
https://gitee.com/cxlzff/fuzz-poc/raw/master/libredwg/decode_preR13_entities_Assertion


Assertion dwg2dxf: decode.c:5801: int decode_preR13_entities(BITCODE_RL, BITCODE_RL, unsigned int, BITCODE_RL, BITCODE_RL, Bit_Chain *, Dwg_Data *): Assertion `!dat->bit' failed. Aborted. 
This is a GitHub Issue
repo:libredwg
owner:LibreDWG
Title : Assertion dwg2dxf: decode.c:5801: int decode_preR13_entities(BITCODE_RL, BITCODE_RL, unsigned int, BITCODE_RL, BITCODE_RL, Bit_Chain *, Dwg_Data *): Assertion `!dat->bit' failed. Aborted. 
Issue date:

--- start body ---
### system info
Ubuntu x86_64, clang 6.0, dwg2dxf([0.12.4.4608](https://github.com/LibreDWG/libredwg/releases/tag/0.12.4.4608))

### Command line
./programs/dwg2dxf -b -m @@ -o /dev/null

###  output
dwg2dxf: decode.c:5801: int decode_preR13_entities(BITCODE_RL, BITCODE_RL, unsigned int, BITCODE_RL, BITCODE_RL, Bit_Chain *, Dwg_Data *): Assertion `!dat->bit' failed.
Aborted

### poc
https://gitee.com/cxlzff/fuzz-poc/raw/master/libredwg/decode_preR13_entities_Assertion


--- end body ---
