NPE in StickyScrollControl.getStickyLineStyleRanges eclipse-platform#1964

When the sticky lines are styled, the linked text widget could already be disposed or null. In this case, the sticky lines must not be styled.

Fixes eclipse-platform#1964

Author: Christopher-Hermann

bundles/org.eclipse.ui.editors/src/org/eclipse/ui/internal/texteditor/stickyscroll/StickyScrollingControl.java

@@ -217,6 +217,9 @@ private String fillLineNumberWithLeadingSpaces(int lineNumber) {
 
 	private void styleStickyLines() {
 		StyledText textWidget= sourceViewer.getTextWidget();
+		if (textWidget == null || textWidget.isDisposed()) {
+			return;
+		}
 
 		List<StyleRange> stickyLinesStyleRanges= new ArrayList<>();
 		int stickyLineTextOffset= 0;