ab215965c6
Since 3f26bdf840, `text_format_string_literal_find` is used to get the
length of the string literal. This can return -1 though and this can
lead to accessing negative index in the string afterwards.
Now, let `text_format_string_literal_find` return 0 (instead of -1) since 0
is never going to be a valid string length anyways.
Pull Request: https://projects.blender.org/blender/blender/pulls/109441