GimpDocument raises Exception: Parasites=0 Strokes=1 for files with vectors

[ismaelharunid]

GimpDocument raises Exception: Parasites=0 Strokes=1 for files with vectors (or in my case, maybe it's not any and all vectors)

For:

doc = GimpDocument(imagepath)
```

Full Exceptuion dump:

bytearray(b'\x00\x00\x00\x01\x00\x00\x00\x03\x00\x00\x00\x08\x00\x00\x00\x1bSelection #1 stroke 1 copy\x00\x00\x00\x00\x9b\x00\x00\x00')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/ismael/miniconda3/lib/python3.7/site-packages/gimpFormats/gimpXcfDocument.py", line 394, in __init__
    self.load(filename)
  File "/home/ismael/miniconda3/lib/python3.7/site-packages/gimpFormats/gimpXcfDocument.py", line 410, in load
    self._decode_(data)
  File "/home/ismael/miniconda3/lib/python3.7/site-packages/gimpFormats/gimpXcfDocument.py", line 432, in _decode_
    self._propertiesDecode_(io)
  File "/home/ismael/miniconda3/lib/python3.7/site-packages/gimpFormats/gimpIOBase.py", line 641, in _propertiesDecode_
    self._propertyDecode_(propertyType,io.getBytes(dataLength))
  File "/home/ismael/miniconda3/lib/python3.7/site-packages/gimpFormats/gimpIOBase.py", line 417, in _propertyDecode_
    self._vectorsDecode_(data)
  File "/home/ismael/miniconda3/lib/python3.7/site-packages/gimpFormats/gimpIOBase.py", line 284, in _vectorsDecode_
    index=gv.fromBytes(data,index)
  File "/home/ismael/miniconda3/lib/python3.7/site-packages/gimpFormats/gimpVectors.py", line 55, in fromBytes
    raise Exception('Parasites=%d Strokes=%d'%(numParasites,numStrokes))
Exception: Parasites=0 Strokes=1

```