failsafe: set cause to generic when fallback mode is activated

Previously when triggering low battery RTL and then losing GPS, the fallback
to Descend would still have low battery as cause.

src/modules/commander/failsafe/framework.cpp

@@ -517,48 +517,62 @@ void FailsafeBase::getSelectedAction(const State &state, const failsafe_flags_s
 			break;
 		}
 
+		returned_state.cause = Cause::Generic;
+
 	// fallthrough
 	case Action::FallbackAltCtrl:
 		if (modeCanRun(status_flags, vehicle_status_s::NAVIGATION_STATE_ALTCTL)) {
 			selected_action = Action::FallbackAltCtrl;
 			break;
 		}
 
+		returned_state.cause = Cause::Generic;
+
 	// fallthrough
 	case Action::FallbackStab:
 		if (modeCanRun(status_flags, vehicle_status_s::NAVIGATION_STATE_STAB)) {
 			selected_action = Action::FallbackStab;
 			break;
 		} // else: fall through here as well. If stabilized isn't available, we most certainly end up in Terminate
 
+		returned_state.cause = Cause::Generic;
+
 	// fallthrough
 	case Action::Hold:
 		if (modeCanRun(status_flags, vehicle_status_s::NAVIGATION_STATE_AUTO_LOITER)) {
 			selected_action = Action::Hold;
 			break;
 		}
 
+		returned_state.cause = Cause::Generic;
+
 	// fallthrough
 	case Action::RTL:
 		if (modeCanRun(status_flags, vehicle_status_s::NAVIGATION_STATE_AUTO_RTL)) {
 			selected_action = Action::RTL;
 			break;
 		}
 
+		returned_state.cause = Cause::Generic;
+
 	// fallthrough
 	case Action::Land:
 		if (modeCanRun(status_flags, vehicle_status_s::NAVIGATION_STATE_AUTO_LAND)) {
 			selected_action = Action::Land;
 			break;
 		}
 
+		returned_state.cause = Cause::Generic;
+
 	// fallthrough
 	case Action::Descend:
 		if (modeCanRun(status_flags, vehicle_status_s::NAVIGATION_STATE_DESCEND)) {
 			selected_action = Action::Descend;
 			break;
 		}
 
+		returned_state.cause = Cause::Generic;
+
 	// fallthrough
 	case Action::Terminate:
 		selected_action = Action::Terminate;