Ignore invalid palettes (#1718)

lib/extensions/palette_to_text.py

@@ -27,6 +27,10 @@ class PaletteToText(InkstitchExtension):
             return
 
         thread_palette = ThreadPalette(palette_file)
+        if not thread_palette.is_gimp_palette:
+            inkex.errormsg(_("Cannot read palette: invalid GIMP palette header"))
+            return
+
         current_layer = self.svg.get_current_layer()
 
         x = 0

lib/threads/catalog.py

@@ -42,6 +42,9 @@ class _ThreadCatalog(Sequence):
             for palette_file in glob(os.path.join(path, 'InkStitch*.gpl')):
                 palette_basename = os.path.basename(palette_file)
                 if palette_basename not in palettes:
+                    palette = ThreadPalette(palette_file)
+                    if not palette.is_gimp_palette:
+                        continue
                     self.palettes.append(ThreadPalette(palette_file))
                     palettes.append(palette_basename)
 

lib/threads/palette.py

@@ -40,8 +40,11 @@ class ThreadPalette(Set):
 
         with open(palette_file, encoding='utf8') as palette:
             line = palette.readline().strip()
+
+            self.is_gimp_palette = True
             if line.lower() != "gimp palette":
-                raise ValueError("Invalid gimp palette header")
+                self.is_gimp_palette = False
+                return
 
             self.name = palette.readline().strip()
             if self.name.lower().startswith('name: ink/stitch: '):