Don't show tooltip if there is nothing to display

We do this because resource is undefined for @room

Signed-off-by: Šimon Brandner <simon.bra.ag@gmail.com>

src/components/views/elements/Pill.js

@@ -274,7 +274,7 @@ class Pill extends React.Component {
             const {yOffset} = this.props;
 
             let tip;
-            if (this.state.hover) {
+            if (this.state.hover && resource) {
                 tip = <Tooltip label={resource} yOffset={yOffset} />;
             }