libcamera: control_serializer: Use explicit ControlTypeNone case

Replace the default case with an explicit ControlTypeNone case in
ControlSerializer::load() to catch omissions when adding new control
types.

A return statement needs to be added to the end of the function to avoid
gcc incorrectly reporting that some exit paths don't contain a return
statement. The compiler will still warn that not all cases are handled
when adding a new control type.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/libcamera/control_serializer.cpp

@@ -361,9 +361,11 @@ ControlValue ControlSerializer::load<ControlValue>(ControlType type,
 		return ControlValue(value);
 	}
 
-	default:
+	case ControlTypeNone:
 		return ControlValue();
 	}
+
+	return ControlValue();
 }
 
 template<>