Introduce variants to represent Error instead of macro.
Fix: -Wextra included -Wsign-compare.
../libgimpthumb/gimp-thumbnail-list.c: In function ‘process_thumbnail’:
../libgimpthumb/gimp-thumbnail-list.c:189:24: warning: comparison of integer expressions of different signedness: ‘GimpThumbState’ and ‘int’ [-Wsign-compare]
189 | if (option_state == STATE_ERROR)
| ^~
../libgimpthumb/gimp-thumbnail-list.c:203:25: warning: comparison of integer expressions of different signedness: ‘GimpThumbState’ and ‘int’ [-Wsign-compare]
203 | if ((option_state == STATE_NONE || state == option_state)
| ^~
Edited by darnuria