fix(Dropdown): check for blur() before calling it Semantic-Org#659

Author: anhpha

src/modules/Dropdown/Dropdown.js

@@ -930,7 +930,10 @@ export default class Dropdown extends Component {
     // https://github.com/Semantic-Org/Semantic-UI-React/issues/627
     // Blur the Dropdown on close so it is blurred after selecting an item.
     // This is to prevent it from re-opening when switching tabs after selecting an item.
-    this._dropdown.blur()
+    //fix(Dropdown): check for blur() before calling it #659
+    if (this._dropdown && typeof this._dropdown.blur === 'function') {
+        this._dropdown.blur()
+    };
 
     // We need to keep the virtual model in sync with the browser focus change
     // https://github.com/Semantic-Org/Semantic-UI-React/issues/692