fix(explore): only show split close button when split is active (#16203)

public/app/features/explore/ExploreToolbar.tsx

@@ -108,9 +108,11 @@ export class UnConnectedExploreToolbar extends PureComponent<Props, {}> {
                 </span>
               )}
             </div>
-            <a className="explore-toolbar-header-close" onClick={() => this.props.closeSplit(exploreId)}>
-              <i className="fa fa-times fa-fw" />
-            </a>
+            {splitted && (
+              <a className="explore-toolbar-header-close" onClick={() => this.props.closeSplit(exploreId)}>
+                <i className="fa fa-times fa-fw" />
+              </a>
+            )}
           </div>
         </div>
         <div className="explore-toolbar-item">