Exporting a Flipper trace should not swallow errors

Summary: Noticed that when creating a flipper trace file, the errors were only shown in the console, but the dialog would hide.

Reviewed By: jknoxville, passy

Differential Revision: D29327500

fbshipit-source-id: 0ec60be28b5e3041f7cacd48ac4bcf13753f7219

desktop/app/src/chrome/ShareSheetExportFile.tsx

@@ -131,7 +131,12 @@ export default class ShareSheetExportFile extends Component<Props, State> {
           requireInteraction: true,
         });
       }
-      this.setState({fetchMetaDataErrors, result: {kind: 'success'}});
+      this.setState({
+        fetchMetaDataErrors,
+        result: fetchMetaDataErrors
+          ? {error: JSON.stringify(fetchMetaDataErrors) as any, kind: 'error'}
+          : {kind: 'success'},
+      });
       this.store.dispatch(unsetShare());
       this.props.logger.trackTimeSince(mark, 'export:file-success');
     } catch (err) {
@@ -145,8 +150,9 @@ export default class ShareSheetExportFile extends Component<Props, State> {
       if (!this.state.runInBackground) {
         // Show the error in UI.
         this.setState({result});
-      }
+      } else {
         this.store.dispatch(unsetShare());
+      }
       this.props.logger.trackTimeSince(mark, 'export:file-error', result);
       throw err;
     }