title: jmeter.extractor.RegexExtractor: Error in pattern
body: <p>I tested my regex in the tree view and it worked fine, but when I actually run the test it's giving me the error in the title.</p>
  
  <p>The pattern I'm using is <code>(?&lt;=\{\"id\":)\d+</code></p>
  
  <p>I have also tried <code>(?&lt;=\{\"id\":)(\d+)</code></p>
  
  <p>The response data looks like this: <code>aaData":[{"id":488,"environment":</code> (I am trying to match <code>488</code>)</p>
  
  <p>I've tried changing the response field to check (I've tried them all), not sure what else could be wrong.</p>