Out-of-bounds read when a multi-line text view string ends with a carriage return

`_gx_multi_line_text_view_display_info_get()` reads one byte past the end of the application's text buffer when the string it is given ends with a carriage return (`\r`). The over-read can also cause callers to advance their index past the end of the string, producing a second over-read in `_gx_multi_line_text_view_string_total_rows_compute()` and a row of text that is not in the source.