TabbedPane: fixed NPE in scroll layout when removing last tab

CHANGELOG.md

@@ -16,7 +16,7 @@ FlatLaf Change Log
 - TabbedPane: Support adding custom components to left and right sides of tabs
   area. (set client property `JTabbedPane.leadingComponent` or
   `JTabbedPane.trailingComponent` to a `java.awt.Component`) (issue #40)
-- TabbedPane: Support closable tabs. (issue #40)
+- TabbedPane: Support closable tabs. (issues #31 and #40)
 - Support painting separator line between window title and content (use UI value
   `TitlePane.borderColor`). (issue #184)
 

flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatTabbedPaneUI.java

@@ -1844,6 +1844,13 @@ public class FlatTabbedPaneUI
 			if( !useMoreButton && (backwardButton == null || forwardButton == null) )
 				return; // should never occur
 
+			if( rects.length == 0 ) {
+				moreTabsButton.setVisible( false );
+				backwardButton.setVisible( false );
+				forwardButton.setVisible( false );
+				return;
+			}
+
 			Rectangle bounds = tabPane.getBounds();
 			Insets insets = tabPane.getInsets();
 			int tabPlacement = tabPane.getTabPlacement();