mesh: Avoid a false maybe-uninitialized compiler warning

An earlier check of the action_field value above the switch statement
already took care of all other possible cases, but that was apparently
too difficult for the compiler to notice. Bring back the default case to
avoid incorrect warnings about the event variable being maybe
uninitialized.

Signed-off-by: Jouni Malinen <j@w1.fi>

wpa_supplicant/mesh_mpm.c

@@ -971,6 +971,13 @@ void mesh_mpm_action_rx(struct wpa_supplicant *wpa_s,
 		else
 			event = CLS_ACPT;
 		break;
+	default:
+		/*
+		 * This cannot be hit due to the action_field check above, but
+		 * compilers may not be able to figure that out and can warn
+		 * about uninitialized event below.
+		 */
+		return;
 	}
 	mesh_mpm_fsm(wpa_s, sta, event);
 }