Don't allow 0 width structure members get added

[mwales]

Version and Platform (required):

• Binary Ninja Version: [4.1.5747 enterprise
• OS: Ubuntu
• OS Version: 22.04
• CPU Architecture: x64

Bug Description:
Created a snippet to create vtable structures using existing information from functions that binary ninja had already analyzed. structure looks messed up afterwards. zznop identified that the type i was adding was 0 width, and that I should instead wrap my function type with a Type.pointer to fix.

Steps To Reproduce:

s = types.StructureBuilder.create()
member_func = bv.read_pointer(addr + i)
cur_func = bv.get_function_at(member_func)
...
s.add_member_at_offset(memberName, cur_func.type, offset_val)
bv.define_user_type(vtable_class_name + "_vtable", s)
​

Fixed by instead doing:

s.add_member_at_offset(memberName, Type.pointer(bv.arch,cur_func.type), offset_val)

Expected Behavior:
Adding 0 width items to structure will probably just create confusion

Screenshots/Video Recording:

[psifertex]

For what it's worth, we already do warn in the UI. We'll do some further discussion internally next week to figure out whether this is something we should address purely with documentation or whether we should do something more like warn or except at the python layer