Hi Henri.
Something isn't working as it should with 1.26.8.13 for me. (1.26.8.12 works just fine.)
As you know I compile your sources myself with only two changes: Turning tcmalloc back on (switch in 00-Common.cmake) and reverting to libpng 1.2 instead of 1.5 (edit of install.xml for sources, and changing version call in PNG.cmake) as Debian still uses 1.2.
Here is reproducible steps for me:
1. Take snapshot
2. Save as file, select file name and folder and hit save.
3. Segfault.
It works normally with the previous source, and both versions has been compiled on a *clean* tree in an empty folder in case you wonder if I learned my lesson.
Log file, stack trace and GDB output attached.