code: public void removeLoadedExtension(Extension extension) {
  		if (extension == null) {
  			throw new IllegalArgumentException("Parameter extension must not be null.");
  		}
  
  		if (loadedExtensions != null && loadedExtensions.contains(extension)) {
  			loadedExtensions.remove(extension);
  			extension.setAddOn(null);
  		}
  	}
docs: Removes the given {@code extension} from the list of loaded extensions of this add-on.
  <p>
  The add-on of the given {@code extension} is set to {@code null}.
  <p>
  The call to this method has no effect if the given {@code extension} does not belong to this add-on.
  
  @param extension the loaded extension of this add-on that should be removed
  @throws IllegalArgumentException if extension is {@code null}
  @since 2.4.0
  @see #addLoadedExtension(Extension)
  @see Extension#setAddOn(AddOn)