protected boolean isContentEmpty() {
			int tabCount = tabPane.getTabCount();
			if( tabCount == 0 )
				return false;

			for( int i = 0; i < tabCount; i++ ) {
				Component c = tabPane.getComponentAt( i );
				if( c != null ) {
					Dimension cs = c.getPreferredSize();
					if( cs.width != 0 || cs.height != 0 )
						return false;
				}
			}

			return true;
		}
Check whether all content components are either {@code null} or have zero preferred size.
<p>
If {@code true}, assume that the tabbed pane is used without any content and
use the size of the tab area (single run) as minimum/preferred size.
flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatTabbedPaneUI.java