There is an issue in the encoding of 3DLINE in pre13.
Test via dwgadd.

cat test.dwgadd
``` 
line (1 2 3) (4 5 6)
```

Command:
```dwgadd -v9 --as r9 -o test.dwg test.dwgadd```

Output:
```
Add entity _3DLINE [8] Decode entity _3DLINE
===========================
Entity number: 8, Type: 21, Addr: 3ef
flag_r11: 0x0 [RC 0]
size: 56 [RS]
layer: -1 [H(RSd) 8]
opts_r11: 0x3 [RSx 0]
          HAS_Z_FIRST(0x1) HAS_Z_SECOND(0x2)
object_map{22} = 8
=> handle: (0.1.22)
start: (0, 1, 2) [3RD 10]
end: (3, 4, 5) [3RD 11]
```
Issue in encoding 3DLINE in preR13
This is a GitHub Issue
repo:libredwg
owner:LibreDWG
Title : Issue in encoding 3DLINE in preR13
Issue date:

--- start body ---
There is an issue in the encoding of 3DLINE in pre13.
Test via dwgadd.

cat test.dwgadd
``` 
line (1 2 3) (4 5 6)
```

Command:
```dwgadd -v9 --as r9 -o test.dwg test.dwgadd```

Output:
```
Add entity _3DLINE [8] Decode entity _3DLINE
===========================
Entity number: 8, Type: 21, Addr: 3ef
flag_r11: 0x0 [RC 0]
size: 56 [RS]
layer: -1 [H(RSd) 8]
opts_r11: 0x3 [RSx 0]
          HAS_Z_FIRST(0x1) HAS_Z_SECOND(0x2)
object_map{22} = 8
=> handle: (0.1.22)
start: (0, 1, 2) [3RD 10]
end: (3, 4, 5) [3RD 11]
```
--- end body ---
