InputHarvester: debug if no widget

If there's no widget found then one of two things will happen: if it's
optional, the program will continue as normal. If it's required, an
exception is thrown. In the latter case we do not need to double warn,
and in the former a debugging statement should be sufficient.

Author: hinerm

src/main/java/org/scijava/widget/AbstractInputHarvester.java

@@ -135,7 +135,7 @@ private <T> WidgetModel addInput(final InputPanel<P, W> inputPanel,
 		final Class<W> widgetType = inputPanel.getWidgetComponentType();
 		final InputWidget<?, ?> widget = widgetService.create(model);
 		if (widget == null) {
-			log.warn("No widget found for input: " + model.getItem().getName());
+			log.debug("No widget found for input: " + model.getItem().getName());
 		}
 		if (widget != null && widget.getComponentType() == widgetType) {
 			@SuppressWarnings("unchecked")