GSettingsBackend: does not crash if the scheme is not found

src/settings/backends/gsettings.py

@@ -4,36 +4,51 @@ from .base import Backend
 
 
 class GSettingsBackend(Backend):
+    def _get_schema(self, schema_name):
+        source = Gio.SettingsSchemaSource.get_default()
+
+        if source.lookup(schema_name, True) is None:
+            print(f"[ERROR] Scheme {schema_name} is not installed")
+            return None
+
+        return Gio.Settings.new(schema_name)
+
     def get_value(self, key, gtype):
         schema_name, key_name = key.rsplit('.', 1)
-        schema = Gio.Settings.new(schema_name)
+        schema = self._get_schema(schema_name)
+
+        if not schema:
+            return None
 
-        print(f"[DEBUG] Получение значения: schema={schema_name}, key={key_name}, gtype={gtype}")
         try:
             value = schema.get_value(key_name)
             return value.unpack()
         except Exception as e:
-            print(f"[ERROR] Ошибка при получении значения {key}: {e}")
+            print(f"[ERROR] Error when getting the value {key}: {e}")
             return None
 
     def get_range(self, key, gtype):
         schema_name, key_name = key.rsplit('.', 1)
-        schema = Gio.Settings.new(schema_name)
+        schema = self._get_schema(schema_name)
+
+        if not schema:
+            return None
 
-        print(f"[DEBUG] Получение значения: schema={schema_name}, key={key_name}, gtype={gtype}")
         try:
             value = schema.get_range(key_name)
             return value.unpack()[1]
         except Exception as e:
-            print(f"[ERROR] Ошибка при получении значения {key}: {e}")
+            print(f"[ERROR] Error when getting the range {key}: {e}")
             return None
 
     def set_value(self, schema_key, value, gtype):
         schema_name, key_name = schema_key.rsplit('.', 1)
-        schema = Gio.Settings.new(schema_name)
+        schema = self._get_schema(schema_name)
+
+        if not schema:
+            return
 
-        print(f"[DEBUG] Установка значения: schema={schema_name}, key={key_name}, value={value}, gtype={gtype}")
         try:
             schema.set_value(key_name, GLib.Variant(gtype, value))
         except Exception as e:
-            print(f"[ERROR] Ошибка при установке значения {schema_key}: {e}")
+            print(f"[ERROR] Error when setting the value {schema_key}: {e}")