[fix] Flight crash in singleplayer (#1565)

Entering a singleplayer world with flight enabled causes this crash.
https://hastebin.com/tufariposu.log

src/main/java/me/zeroeightsix/kami/module/modules/movement/Flight.kt

@@ -47,6 +47,7 @@ object Flight : Module() {
 
     init {
         listener<PlayerTravelEvent> {
+            if (mc.player == null) return@listener
             when (mode.value) {
                 FlightMode.STATIC -> {
                     mc.player.capabilities.isFlying = false
@@ -101,4 +102,4 @@ object Flight : Module() {
             if (mode.value == FlightMode.PACKET && it.packet is SPacketCloseWindow) it.cancel()
         }
     }
-}
+}