cs_themes.py: Don't print an error if metadata.json is missing

This was triggered on any theme installed in ~/.local/share/themes
or ~/.themes.

Author: clefebvre

files/usr/share/cinnamon/cinnamon-settings/bin/Spices.py

@@ -420,8 +420,9 @@ def _load_metadata(self):
                         metadata['writable'] = os.access(subdirectory, os.W_OK)
                         self.meta_map[uuid] = metadata
                     except Exception as detail:
-                        print(detail)
-                        print("Skipping %s: there was a problem trying to read metadata.json" % uuid)
+                        if not self.themes:
+                            print(detail)
+                            print("Skipping %s: there was a problem trying to read metadata.json" % uuid)
             else:
                 print("%s does not exist! Creating it now." % directory)
                 subprocess.call(["mkdir", "-p", directory])