Handle command_line missing discovery_info (#116873)

* command_line: Do not lead to erroring out code indexing None or empty discovery_info

* Apply suggestions from code review

Co-authored-by: Franck Nijhof <frenck@frenck.nl>

---------

Co-authored-by: Erik Montnemery <erik@montnemery.com>
Co-authored-by: Franck Nijhof <frenck@frenck.nl>

homeassistant/components/command_line/switch.py

@@ -37,6 +37,8 @@ async def async_setup_platform(
 ) -> None:
     """Find and return switches controlled by shell commands."""
 
+    if not discovery_info:
+        return
     switches = []
     discovery_info = cast(DiscoveryInfoType, discovery_info)
     entities: dict[str, dict[str, Any]] = {