Fix missing background color in GroupFilterPanel

res/css/structures/_GroupFilterPanel.scss

@@ -14,7 +14,14 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
+.mx_MatrixChat--with-avatar {
+    .mx_GroupFilterPanel {
+        background-color: transparent;
+    }
+}
+
 .mx_GroupFilterPanel {
+    background-color: $groupFilterPanel-bg-color;
     flex: 1;
     cursor: pointer;
     position: relative;