textureFillBackground did not restore depth mask gl state

various gl functions are disabled to allow background render, then
re-enabled at the end of the method, however depth mask was left
disabled

Author: philjord

src/javax/media/j3d/JoglPipeline.java

@@ -7361,6 +7361,9 @@ void textureFillBackground(Context ctx, float texMinU, float texMaxU, float texM
         gl.glMatrixMode(GL2.GL_MODELVIEW);
         // Restore attributes
         gl.glPopAttrib();
+        
+        // restore writing to the depth buffer
+        gl.glDepthMask(true); 
 
     }