Fix crashes on invalid regex

Summary:
**Problem:**
When you type an invalid regex into the input field of the RNTester app, it crashes. What's worse is that it remembers the input string so refreshing the view doesn't get rid of the error. Observe:
https://pxl.cl/jdm3

Reviewed By: yungsters

Differential Revision: D10349249

fbshipit-source-id: aab5977bd47271e9a4ff6202c93b47550da778d2

RNTester/js/RNTesterExampleList.js

@@ -75,7 +75,18 @@ const renderSectionHeader = ({section}) => (
 class RNTesterExampleList extends React.Component<Props, $FlowFixMeState> {
   render() {
     const filterText = this.props.persister.state.filter;
-    const filterRegex = new RegExp(String(filterText), 'i');
+    let filterRegex = /.*/;
+
+    try {
+      filterRegex = new RegExp(String(filterText), 'i');
+    } catch (error) {
+      console.warn(
+        'Failed to create RegExp: %s\n%s',
+        filterText,
+        error.message,
+      );
+    }
+
     const filter = example =>
       /* $FlowFixMe(>=0.68.0 site=react_native_fb) This comment suppresses an
        * error found when Flow v0.68 was deployed. To see the error delete this