Exception raised when string parser dereferences end iterator

In certain cases in newer photoshop code, I noticed the string parser will step its string iterator to end or beyond and then dereference it, which subsequently raises an exception. May be the same issue as https://github.com/adobe/svg-native-viewer/issues/204.

Start by locating the string parser and reproducing the reported failure with the newer Photoshop-generated SVG Native input. Trace cases where the iterator reaches the end or moves beyond it, then verify that parsing completes without dereferencing an invalid iterator and that the reported case is covered by a regression check.

Written by the indexing model from the issue text.