Fix setData null parameter handling and resource cleanup

Author: riccardobl

jme3-core/src/main/java/com/jme3/shader/bufferobject/BufferObject.java

@@ -165,6 +165,13 @@ public void initializeEmpty(int length) {
      * @param data ByteBuffer containing the data to pass
      */
     public void setData(ByteBuffer data) {
+        if (data == null) {
+            if (this.data != null) {
+                BufferUtils.destroyDirectBuffer(this.data);
+                this.data = null;
+            }
+            return;
+        }
         ByteBuffer source = data == this.data ? data.duplicate() : data;
         ByteBuffer oldData = this.data;
 

jme3-core/src/test/java/com/jme3/shader/bufferobject/DirtyRegionsIteratorTest.java

@@ -3,6 +3,7 @@
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.nio.ByteBuffer;
@@ -88,4 +89,26 @@ public void testSetDataHandlesSelfAlias() {
         assertEquals((byte) 0x33, result.get());
         assertEquals((byte) 0x44, result.get());
     }
+
+    @Test
+    public void testSetDataNullClearsBuffer() {
+        BufferObject bo = new BufferObject();
+        ByteBuffer source = ByteBuffer.allocateDirect(4);
+        source.put(new byte[]{1, 2, 3, 4});
+        source.flip();
+        bo.setData(source);
+        assertEquals(4, bo.getData().remaining());
+
+        bo.setData(null);
+        // getData() auto-allocates an empty buffer when internal data is null
+        assertEquals(0, bo.getData().remaining());
+    }
+
+    @Test
+    public void testSetDataNullOnEmptyBufferObject() {
+        BufferObject bo = new BufferObject();
+        // Should not throw when internal buffer is already null
+        bo.setData(null);
+        assertEquals(0, bo.getData().remaining());
+    }
 }