Fix NPE in dimension_type registry handler in 26.1->1.21.11 (#1242)

Author: roggy666

common/src/main/java/com/viaversion/viabackwards/protocol/v26_1to1_21_11/Protocol26_1To1_21_11.java

@@ -89,9 +89,11 @@ protected void registerPackets() {
         // Remove new environment attributes
         registryDataRewriter.addHandler("dimension_type", (key, tag) -> {
             final CompoundTag attributes = tag.getCompoundTag("attributes");
-            removeNamespaced(attributes, "visual/block_light_tint");
-            removeNamespaced(attributes, "visual/night_vision_color");
-            removeNamespaced(attributes, "visual/ambient_light_color");
+            if (attributes != null) {
+                removeNamespaced(attributes, "visual/block_light_tint");
+                removeNamespaced(attributes, "visual/night_vision_color");
+                removeNamespaced(attributes, "visual/ambient_light_color");
+            }
         });
 
         // Move around entity variant names and sounds