Fixed unexpected error

app/assets/javascripts/components/features/compose/components/compose_form.jsx

@@ -85,12 +85,12 @@ const ComposeForm = React.createClass({
   },
 
   componentDidUpdate (prevProps) {
-    if ((!prevProps.in_reply_to && this.props.in_reply_to) || prevProps.in_reply_to.get('id') !== this.props.in_reply_to.get('id')) {
+    if ((prevProps.in_reply_to === null && this.props.in_reply_to !== null) || (prevProps.in_reply_to !== null && this.props.in_reply_to !== null && prevProps.in_reply_to.get('id') !== this.props.in_reply_to.get('id'))) {
       // If replying to zero or one users, places the cursor at the end of the textbox.
       // If replying to more than one user, selects any usernames past the first;
       // this provides a convenient shortcut to drop everyone else from the conversation.
       const selectionStart = this.props.text.search(/\s/) + 1;
-      const selectionEnd = this.props.text.length;
+      const selectionEnd   = this.props.text.length;
 
       this.autosuggestTextarea.textarea.setSelectionRange(selectionStart, selectionEnd);
       this.autosuggestTextarea.textarea.focus();