clear min-height on timeline resets and other occasions where we load it

src/components/structures/TimelinePanel.js

@@ -935,6 +935,11 @@ var TimelinePanel = React.createClass({
             {windowLimit: this.props.timelineCap});
 
         const onLoaded = () => {
+            // clear the timeline min-height when
+            // (re)loading the timeline
+            if (this.refs.messagePanel) {
+                this.refs.messagePanel.clearTimelineHeight();
+            }
             this._reloadEvents();
 
             // If we switched away from the room while there were pending