Fix TypeError when `signTypedData` throws (#9596)

If the `signTypedData` background function threw an exception, it would
return `undefined` to the UI, which would throw another exception in
the UI. It now re-throws the error if an error is thrown, which
allows the UI to handle the error.

I'm not sure why this might fail, and I'm not sure we're handling this
failure well, but this is an improvement at least.

app/scripts/metamask-controller.js

@@ -1414,7 +1414,7 @@ export default class MetamaskController extends EventEmitter {
     } catch (error) {
       log.info('MetaMaskController - eth_signTypedData failed.', error)
       this.typedMessageManager.errorMessage(msgId, error)
-      return undefined
+      throw error
     }
   }