Added in support for automatically going to the "BrandSelector" page if there is no brand found on sign in.

src/screens/SignIn.js

@@ -17,6 +17,13 @@ export default class SignIn extends Component {
     this.passwordRef = React.createRef();
   }
 
+  componentDidMount() {
+    // If the brand is not selected, then resort back to the brand selector
+    if (useStore.getState().brandInfo === null) {
+      this.props.navigation.replace('BrandSelector');
+    }
+  }
+
   render() {
     return (
       <View style={pageStyle.container}>