Workaround for atlassian/react-beautiful-dnd#273

Fix two bugs in Riot due to a single bug in react-b-dnd

Fixes vector-im/riot-web#6253
Fixes vector-im/riot-web#6156

src/components/structures/TagPanel.js

@@ -84,7 +84,7 @@ const TagPanel = React.createClass({
         }
     },
 
-    onClick(e) {
+    onMouseDown(e) {
         dis.dispatch({action: 'deselect_tags'});
     },
 
@@ -128,7 +128,9 @@ const TagPanel = React.createClass({
             <GeminiScrollbar
                 className="mx_TagPanel_scroller"
                 autoshow={true}
-                onClick={this.onClick}
+                // XXX: Use onMouseDown as a workaround for https://github.com/atlassian/react-beautiful-dnd/issues/273
+                // instead of onClick. Otherwise we experience https://github.com/vector-im/riot-web/issues/6253
+                onMouseDown={this.onMouseDown}
             >
                 <Droppable
                     droppableId="tag-panel-droppable"