Room header: do not collapse avatar or facepile (#11866)

* Room header: do not collapse avatar or facepile

* comment

res/css/structures/_RightPanel.pcss

@@ -25,6 +25,7 @@ limitations under the License.
     box-sizing: border-box;
     height: 100%;
     contain: strict;
+    background-color: var(--cpd-color-bg-canvas-default);
 
     .mx_RoomView_MessageList {
         padding: 14px 18px; /* top and bottom is 4px smaller to balance with the padding set above */

res/css/views/rooms/_RoomHeader.pcss

@@ -83,8 +83,19 @@ limitations under the License.
     cursor: pointer;
     user-select: none;
 
+    /* RoomAvatar doesn't pass classes down to avatar
+    So set style here
+    using div because compound classes are not stable */
+    > div {
+        flex-shrink: 0;
+    }
+
     &:hover {
         color: $primary-content;
         background: var(--cpd-color-bg-subtle-primary);
     }
 }
+
+.mx_RoomHeader .mx_BaseAvatar {
+    flex-shrink: 0;
+}