Fix Button 3D content swap

gui/src/3D/controls/button3D.ts

@@ -124,6 +124,9 @@ export class Button3D extends AbstractButton3D {
             this._facadeTexture.rootContainer.scaleY = this._contentScaleRatio;
             this._facadeTexture.premulAlpha = true;
         }
+        else {
+            this._facadeTexture.rootContainer.clearControls();
+        }
 
         this._facadeTexture.addControl(value);