title: Deleting a handle previously created
body: <p>I am trying to delete a handle <code>handles.roi1</code> that I created. </p>
  
  <p>I already tried to use the function <code>delete</code>: </p>
  
  <pre><code>delete(handles.roi1)
  </code></pre>
  
  <p>but it gave me this error:</p>
  
  <pre><code>Argument must contain a string. 
  </code></pre>
  
  <p>My purpose is to delete a handle like I have never created it. </p>
  
  <p>Do you have any suggestion or tips how can I do it?</p>
  
  <hr>
  
  <p>Maybe I didn't express correctly...</p>
  
  <p>I am doing a GUI, where I define in one button <code>handles.roi1</code>, but then I want to delete it on another button. This because, on that button I do:</p>
  
  <pre><code>try a=handles.roi1;
  catch
      b=11;
  </code></pre>
  
  <p>And I want that it goes to the <code>catch</code>. I tried to do the <code>handles = rmfield(handles, 'roi1');</code> but it didn't work.</p>