JSON Path Input Dialog Closes when validation failed

## Expected Behavior
If a validation of a form to create a JSON Path Input fails, it should remain open so a user can correct the mistake

## Current Behavior
The validation happens on the server side after the modal is closed. The error message is not helpful, and the user must start guessing the actual problem.

## Possible Solution
Validate the JSON Path parameter on the frontend side to prevent closing the modal.

## Steps to Reproduce (for bugs)
1. Go to the Inputs Page
2. Open the JSON Path Input, creating a modal
3. Add a name for the input
4. for **JSON path of data to extract** fill out `$.`
5. Try to save the Input

## Your Environment
* Graylog Version: Graylog 6.2.0-SNAPSHOT+7845ab9 on server (Eclipse Adoptium 17.0.13 on Linux 5.15.0-1071-aws)