Can not create Shapefile with NULL type

[jmikulasek]

I tried to create a Shapefile of NULL type with several records. When I tried to save it I got this exception:

File "C:\Projects\Sources\Arboretum\src\shapefile.py", line 1030, in save
    self.saveShx(target)
File "C:\Projects\Sources\Arboretum\src\shapefile.py", line 993, in saveShx
    self.shapeType = self._shapes[0].shapeType
IndexError: list index out of range

The reason is this condition: if not self.shapeType: in the Writer.saveShp and Writer.saveShx methods. When the condition is changed to if self.shapeType is None: the Shapefile is saved successfully.

[micahcochran]

Will PR #60 fix this issue?

[karimbahgat]

Several recent commits has resolved the issue of saving empty shapefiles. Nevertheless, the suggested change is more correct and implemented in 62e0abe.