Fix bug where import after error continues failing (#463)

Steps to reproduce:
1. Open https://www.speedscope.app/
2. Try to import an invalid file such as [invalid.json](https://github.com/jlfwong/speedscope/files/14167326/invalid.json). The page says "Something went wrong. Check the JS console for more details."
3. Now try to import a valid file such as [simple.json](https://github.com/jlfwong/speedscope/files/14167335/simple.json). The page says "Something went wrong. Check the JS console for more details." even though this second file is valid.

Explanation of the fix (copied from the commit message):
> We need to clear the error flag, otherwise once there is an error and we display "Something went wrong" we will keep displaying that forever even when the user imports a valid file.

src/views/application.tsx

@@ -168,6 +168,7 @@ export type ApplicationProps = {
 
 export class Application extends StatelessComponent<ApplicationProps> {
   private async loadProfile(loader: () => Promise<ProfileGroup | null>) {
+    this.props.setError(false)
     this.props.setLoading(true)
     await new Promise(resolve => setTimeout(resolve, 0))