Colors are null in Section onPaint and cause null pointer exception eclipse-platform#2972

Changed code found in Section.class (onPaint) which lets
null values slip through and cause null pointer exception.

Fixes eclipse-platform#2972

Author: selundqma

bundles/org.eclipse.ui.forms/src/org/eclipse/ui/forms/widgets/Section.java

@@ -316,7 +316,8 @@ private void putTitleBarColor(String key, Color color) {
 	@Override
 	protected void onPaint(PaintEvent e) {
 		Color bg = (titleColors != null) ? titleColors.getOrDefault(COLOR_BG, getBackground()) : getBackground();
-		Color fg = (titleColors != null) ? getTitleBarForeground() : getForeground();
+		Color fg = (titleColors != null) ? (getTitleBarForeground() != null
+				? getTitleBarForeground() : getForeground()) : getForeground();
 		Color border = (titleColors != null) ? titleColors.getOrDefault(COLOR_BORDER, fg) : fg;
 
 		GC gc = e.gc;