Raise exception if fallback is not found (#2494)

Fixes #2290

## Checklist

- [/] I have added
[tests](https://www.cursorless.org/docs/contributing/test-case-recorder/)
- [/] I have updated the
[docs](https://github.com/cursorless-dev/cursorless/tree/main/docs) and
[cheatsheet](https://github.com/cursorless-dev/cursorless/tree/main/cursorless-talon/src/cheatsheet)
- [/] I have not broken the cheatsheet

cursorless-talon/src/fallback.py

@@ -56,6 +56,7 @@ def perform_fallback(fallback: dict):
         return action_callback()
     except ValueError as ex:
         actions.app.notify(str(ex))
+        raise ex
 
 
 def get_action_callback(fallback: dict) -> Callable: