title: combo box connect signal should not be triggered when the combo box is empty
body: <p>I have connected a combo box to a slot on currentIndexChanged value.</p>
  
  <p>The issue i am facing is that when i clear all the items from the combo box than also the event gets triggered.</p>
  
  <p>Whenever i clear all the items from the combo box i do not want the function to execute.</p>
  
  <p>what i though of was to add a if condition when the number of elements of the combo box is 0 , but i could not find any member function in the combo box that would return the number of elements in the combo box.</p>
  
  <p>If there is a better way to do this please let me know. </p>
  
  <pre><code> connect(comboBoxFunctions, qOverload&lt;int&gt;(&amp;QComboBox::currentIndexChanged), 
   this, &amp;WavefrontRenderer::AddContainerFunctionProperty);
  </code></pre>