Blender Git Loki

partial fix [#23265] matrix_world rna path is visible but returns 0 to drivers without error however accessed
this report raised a number of problems with rna paths, while we still dont have multi-dimensional array access, invalid paths were being accepted which confused things.

rna path resolving code was accepting all sorts of invalid input because atoi() just returns 0 for non numeric input.
now check if 0 number == '0' character.