Fix frozen variable getter

Author: letsgoawaydev

core/src/main/java/org/geysermc/geyser/session/GeyserSession.java

@@ -1209,7 +1209,7 @@ protected void tick() {
                 isInWorldBorderWarningArea = false;
             }
 
-            if (!isFrozen()) {
+            if (!frozen) {
                 for (Tickable entity : entityCache.getTickableEntities()) {
                     entity.tick();
                 }