UI: Fix transform dialog not being closable

If the user clicked away from the source, while the transform dialog is open,
the whole dialog would be disabled. The user then couldn't click close or
press escape to close the dialog. The only way for them to close it was to
click on another source to re-enable it.

UI/window-basic-transform.cpp

@@ -144,7 +144,9 @@ void OBSBasicTransform::SetItemQt(OBSSceneItem newItem)
 	if (item)
 		RefreshControls();
 
-	setEnabled(!!item);
+	bool enable = !!item;
+	ui->container->setEnabled(enable);
+	ui->buttonBox->button(QDialogButtonBox::Reset)->setEnabled(enable);
 }
 
 void OBSBasicTransform::OBSChannelChanged(void *param, calldata_t *data)