Avoid crash if unable to modify the model config file (#3824)

* fix whitespace; remove invisible characters
* log error and proceed if unable to modify the model config

invokeai/backend/model_management/model_manager.py

@@ -140,14 +140,14 @@ Layout of the `models` directory:
 
  models
  ├── sd-1
- │   ├── controlnet
- │   ├── lora
- │   ├── main
- │   └── embedding
+ │   ├── controlnet
+ │   ├── lora
+ │   ├── main
+ │   └── embedding
  ├── sd-2
- │   ├── controlnet
- │   ├── lora
- │   ├── main
+ │   ├── controlnet
+ │   ├── lora
+ │   ├── main
  │   └── embedding
  └── core
      ├── face_reconstruction
@@ -824,10 +824,14 @@ class ModelManager(object):
         assert config_file_path is not None,'no config file path to write to'
         config_file_path = self.app_config.root_path / config_file_path
         tmpfile = os.path.join(os.path.dirname(config_file_path), "new_config.tmp")
+        try:
             with open(tmpfile, "w", encoding="utf-8") as outfile:
                 outfile.write(self.preamble())
                 outfile.write(yaml_str)
             os.replace(tmpfile, config_file_path)
+        except OSError as err:
+            self.logger.warning(f"Could not modify the config file at {config_file_path}")
+            self.logger.warning(err)
 
     def preamble(self) -> str:
         """
@@ -986,4 +990,3 @@ class ModelManager(object):
             successfully_installed.update(installed)
         self.commit()
         return successfully_installed
-