slicer Function: No check on return value for get_instruction_start()

[kristopax]

While running this plugin at one of the addresses within the _start function on the latest dev version of Binary Ninja in the UI on a macOS version /bin/ls, I get the following python error:

Traceback (most recent call last):
File "/Users/bk/Documents/projects/binja/build/out/binaryninja.app/Contents/MacOS/plugins/../../Resources/python/binaryninja/plugin.py", line 153, in _address_action
action(view_obj, addr)
File "/Users/bk/Library/Application Support/Binary Ninja/repositories/community/plugins/c3r34lk1ll3r_Instruction_Slicer/init.py", line 48, in s_f
slicer(bv,address,'F')
File "/Users/bk/Library/Application Support/Binary Ninja/repositories/community/plugins/c3r34lk1ll3r_Instruction_Slicer/init.py", line 13, in slicer
instr = ml[ml.get_instruction_start(address)].ssa_form
File "/Users/bk/Documents/projects/binja/build/out/binaryninja.app/Contents/MacOS/plugins/../../Resources/python/binaryninja/mediumlevelil.py", line 874, in getitem
if i < -len(self) or i >= len(self):
TypeError: '<' not supported between instances of 'NoneType' and 'int'
Traceback (most recent call last):
File "/Users/bk/Documents/projects/binja/build/out/binaryninja.app/Contents/MacOS/plugins/../../Resources/python/binaryninja/plugin.py", line 153, in _address_action
action(view_obj, addr)
File "/Users/bk/Library/Application Support/Binary Ninja/repositories/community/plugins/c3r34lk1ll3r_Instruction_Slicer/init.py", line 46, in s_b
slicer(bv,address,'B')
File "/Users/bk/Library/Application Support/Binary Ninja/repositories/community/plugins/c3r34lk1ll3r_Instruction_Slicer/init.py", line 13, in slicer
instr = ml[ml.get_instruction_start(address)].ssa_form
File "/Users/bk/Documents/projects/binja/build/out/binaryninja.app/Contents/MacOS/plugins/../../Resources/python/binaryninja/mediumlevelil.py", line 874, in getitem
if i < -len(self) or i >= len(self):
TypeError: '<' not supported between instances of 'NoneType' and 'int'

It looks like the call to get_instruction_start(address) returns None and the slicer function does not handle this case.

Here is the address and instruction within the _start function at which I selected a Forward slice that produced the error:

100004096 lea rax, [rbp-0x240 {var_248}]