Fix layout when resizing the list width

res/css/views/rooms/_RoomList2.scss

@@ -17,6 +17,8 @@ limitations under the License.
 // TODO: Rename to mx_RoomList during replacement of old component
 
 .mx_RoomList2 {
+    width: calc(100% - 16px); // 16px of artificial right-side margin (8px is overflowed from the sublists)
+
     // Create a column-based flexbox for the sublists. That's pretty much all we have to
     // worry about in this stylesheet.
     display: flex;

res/css/views/rooms/_RoomSublist2.scss

@@ -159,7 +159,7 @@ limitations under the License.
             // either side of the list. We define this after the positioning to
             // trick the browser.
             margin-left: 4px;
-            margin-right: 8px;
+            margin-right: 4px;
         }
     }