fix(Backtrack): npe by race condition

fixes #7289

Author: 1zun4

src/main/kotlin/net/ccbluex/liquidbounce/features/module/modules/combat/backtrack/ModuleBacktrack.kt

@@ -146,18 +146,18 @@ object ModuleBacktrack : ClientModule("Backtrack", Category.COMBAT) {
         val positionPacket = packet is EntityPositionS2CPacket && packet.entityId == target?.id
         val syncPacket = packet is EntityPositionSyncS2CPacket && packet.id == target?.id
         if (entityPacket || positionPacket || syncPacket) {
-            val pos = if (packet is EntityS2CPacket) {
-                position?.withDelta(packet.deltaX.toLong(), packet.deltaY.toLong(), packet.deltaZ.toLong())
-            } else if (packet is EntityPositionS2CPacket) {
-                Vec3d(packet.change.position.x, packet.change.position.y, packet.change.position.z)
-            } else {
-                (packet as EntityPositionSyncS2CPacket).values.position()
+            val pos = when (packet) {
+                is EntityS2CPacket ->
+                    position?.withDelta(packet.deltaX.toLong(), packet.deltaY.toLong(), packet.deltaZ.toLong())
+                is EntityPositionS2CPacket ->
+                    Vec3d(packet.change.position.x, packet.change.position.y, packet.change.position.z)
+                else -> (packet as EntityPositionSyncS2CPacket).values.position()
             }
-
             position?.setPos(pos)
 
             // Is the target's actual position closer than its tracked position?
-            if (target!!.squareBoxedDistanceTo(player, pos!!) < target!!.squaredBoxedDistanceTo(player)) {
+            val target = target ?: return@handler
+            if (target.squareBoxedDistanceTo(player, pos!!) < target.squaredBoxedDistanceTo(player)) {
                 // Process all packets. We want to be able to hit the enemy, not the opposite.
                 processPackets(true)
                 // And stop right here. No need to cancel further packets.