fix the merge script to correctly display models sorted by base

Author: Lincoln Stein

invokeai/frontend/merge/merge_diffusers.py

@@ -131,6 +131,7 @@ def create(self):
             values=[
                 "Models Built on SD-1.x",
                 "Models Built on SD-2.x",
+                "Models Built on SDXL",
             ],
             value=[self.current_base],
             columns=4,
@@ -309,7 +310,7 @@ def validate_field_values(self) -> bool:
         else:
             return True
 
-    def get_model_names(self, base_model: Optional[BaseModelType] = None) -> List[str]:
+    def get_model_names(self, base_model: BaseModelType = BaseModelType.StableDiffusion1) -> List[str]:
         model_names = [
             info["model_name"]
             for info in self.model_manager.list_models(model_type=ModelType.Main, base_model=base_model)
@@ -318,7 +319,8 @@ def get_model_names(self, base_model: Optional[BaseModelType] = None) -> List[st
         return sorted(model_names)
 
     def _populate_models(self, value=None):
-        base_model = tuple(BaseModelType)[value[0]]
+        bases = ["sd-1", "sd-2", "sdxl"]
+        base_model = BaseModelType(bases[value[0]])
         self.model_names = self.get_model_names(base_model)
 
         models_plus_none = self.model_names.copy()