Fixes NPE in StyledText on DPI Resizing

fixes #2320

Author: N1k145

bundles/org.eclipse.swt/Eclipse SWT Custom Widgets/common/org/eclipse/swt/custom/StyledText.java

@@ -10879,8 +10879,10 @@ public static void updateAndRefreshCarets(StyledText styledText, Consumer<Caret>
 	Set<Caret> caretSet = new HashSet<>();
 	caretSet.add(styledText.getCaret());
 	caretSet.add(styledText.defaultCaret);
-	for (Caret caret : styledText.carets) {
-		caretSet.add(caret);
+	if (styledText.carets != null) {
+		for (Caret caret : styledText.carets) {
+			caretSet.add(caret);
+		}
 	}
 	caretSet.forEach(caretUpdater);