@Override
	protected void cancelCallback() {
		setStatusText("");
		close();
	}
This method gets called when the user clicks on the OK Button.  The base
class calls this method.  This method will invoke {@link #applyChanges()} 
and close dialog if that method returns true.  If false is returned, the
{@link #applyChanges()} method should display a status message to indicate
the failure.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/function/AbstractEditFunctionSignatureDialog.java