Unfocus children in Group#clearChildren() (#6423)

* Add Group#clearChildren(boolean unfocus)

* CHANGES note for breaking change.

* Change clearChildren without args to unfocus.

* Typo..

Co-authored-by: Nathan Sweet <nathan.sweet@gmail.com>

CHANGES

@@ -1,6 +1,7 @@
 [1.9.15]
 - [BREAKING CHANGE] Requires Java 7 or above
 - [BREAKING CHANGE] API Change: Scaling is now an object instead of an enum. This may change behavior when used with serialization.
+- [BREAKING CHANGE] Group#clearChildren() now unfocuses the actors. Added Group#clearChildren(boolean unfocus) for when this isn't wanted. #6423
 - Scene2d.ui: Added new ParticleEffectActor to use particle effects on Stage
 - API addition: iOS: Added HdpiMode option to IOSApplicationConfiguration to allow users to set whether they want to work in logical or raw pixels (default logical).
 - Fix for #6377 Gdx.net.openURI not working with targetSdk 30

gdx/src/com/badlogic/gdx/scenes/scene2d/Group.java

@@ -349,11 +349,20 @@ public Actor removeActorAt (int index, boolean unfocus) {
 		return actor;
 	}
 
-	/** Removes all actors from this group. */
+	/** Removes all actors from this group and unfocuses them. Calls {@link #clearChildren(boolean)} with true. */
 	public void clearChildren () {
+		clearChildren(true);
+	}
+
+	/** Removes all actors from this group. */
+	public void clearChildren (boolean unfocus) {
 		Actor[] actors = children.begin();
 		for (int i = 0, n = children.size; i < n; i++) {
 			Actor child = actors[i];
+			if (unfocus) {
+				Stage stage = getStage();
+				if (stage != null) stage.unfocus(child);
+			}
 			child.setStage(null);
 			child.setParent(null);
 		}