There are 3 fixes here:
1. First, searching for "\"GimpFont\"" to determine whether or not this is a new
format text parasite is not enough, because this string can be found in a
text layer with "GimpFont" only as contents. It will serialize as:
> (text "GimpFont")
Instead search for "(font \"GimpFont\"" which cannot be created as part of
the text contents because of the unprotected double quotes).
2. We must verify that strstr() did not return NULL when searching for markup
delimiters. It may happen if the parasite contents is invalid (we must always
assume it can be, since it's user data).
3. When deserialization of a text from parasite fails (e.g. because parasite
doesn't actually exist or its format is wrong), still make sure the GimpText
has a font (setting the standard one before deserializing). Otherwise GIMP
crashes down the line.
For this, I also had to fix gimp_config_deserialize_object(): the object type
name must be parsed even if an object was already set in a GObject property.
ed4c50ce2e