fix: processorExtent can be null in editsession

- fixes #2375

worldedit-core/src/main/java/com/fastasyncworldedit/core/util/ExtentTraverser.java

@@ -4,6 +4,7 @@ import com.sk89q.worldedit.extent.AbstractDelegateExtent;
 import com.sk89q.worldedit.extent.Extent;
 
 import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import java.lang.reflect.Field;
 
 public class ExtentTraverser<T extends Extent> {
@@ -24,6 +25,7 @@ public class ExtentTraverser<T extends Extent> {
         return root != null;
     }
 
+    @Nullable
     public T get() {
         return root;
     }
@@ -50,6 +52,7 @@ public class ExtentTraverser<T extends Extent> {
     }
 
     @SuppressWarnings("unchecked")
+    @Nullable
     public <U> U findAndGet(Class<U> clazz) {
         ExtentTraverser<Extent> traverser = find(clazz);
         return (traverser != null) ? (U) traverser.get() : null;

worldedit-core/src/main/java/com/sk89q/worldedit/EditSession.java

@@ -529,10 +529,12 @@ public class EditSession extends PassthroughExtent implements AutoCloseable {
         //FAWE start - ExtentTraverser & MaskingExtents
         MaskingExtent maskingExtent = new ExtentTraverser<>(getExtent()).findAndGet(MaskingExtent.class);
         if (maskingExtent == null) {
-            ExtentTraverser<ExtentBatchProcessorHolder> processorExtent =
-                    new ExtentTraverser<>(getExtent()).find(ExtentBatchProcessorHolder.class);
+            ExtentBatchProcessorHolder processorExtent =
+                    new ExtentTraverser<>(getExtent()).findAndGet(ExtentBatchProcessorHolder.class);
+            if (processorExtent != null) {
                 maskingExtent =
-                    new ProcessorTraverser<>(processorExtent.get().getProcessor()).find(MaskingExtent.class);
+                        new ProcessorTraverser<>(processorExtent.getProcessor()).find(MaskingExtent.class);
+            }
         }
         return maskingExtent != null ? maskingExtent.getMask() : null;
         //FAWE end