add break to StartupCoordinationState_RUNNING case, as implicit fallthrough is not required and causes warning as error compile issue (#290)

Author: SheaFixstars

src/startup_coordinator.c

@@ -302,6 +302,7 @@ static void StartupCoordinator_handle_start_time_proposal(StartupCoordinator *se
     case StartupCoordinationState_RUNNING:
       // Should not be possible.
       validate(false);
+      break;
     case StartupCoordinationState_HANDSHAKING:
       // This is possible. Our node might be still handshaking with another neighbor.
       // Intentional fall-through