Treat a world list checksum of 0 as 1

This fixes a 1 in 2^32 chance that we'll fail to fetch the world list on
startup.

Of course, updating the player counts will still be borked if we get a
collision, but at least the client won't break entirely.

Signed-off-by: Graham <gpe@openrs2.org>

game/src/main/kotlin/org/openrs2/game/net/login/LoginChannelHandler.kt

@@ -82,7 +82,15 @@ public class LoginChannelHandler @Inject constructor(
     private fun handleRequestWorldList(ctx: ChannelHandlerContext, msg: LoginRequest.RequestWorldList) {
         val (worlds, players) = cluster.getWorldList()
 
-        val checksum = worlds.hashCode()
+        var checksum = worlds.hashCode()
+
+        /*
+         * Fix a 1 in 2^32 chance that we'll fail to fetch the original world
+         * list on startup.
+         */
+        if (checksum == 0) {
+            checksum = 1
+        }
 
         val worldList = if (checksum != msg.checksum) {
             WorldListResponse.WorldList(worlds, checksum)