Fix null pointer exception in prediction API when using multitouch

For handling partial failures, the precition library would free
the resources and return null; however, it was not checked whether
the resource existed before recycling it, which caused null
pointer exceptions.

Test: manual
Bug: 256228049
Change-Id: I017149f26d415edac4797be2a87764fbe73481f5
diff --git a/input/input-motionprediction/src/main/java/androidx/input/motionprediction/kalman/MultiPointerPredictor.java b/input/input-motionprediction/src/main/java/androidx/input/motionprediction/kalman/MultiPointerPredictor.java
index c517321..1b0b3cd 100644
--- a/input/input-motionprediction/src/main/java/androidx/input/motionprediction/kalman/MultiPointerPredictor.java
+++ b/input/input-motionprediction/src/main/java/androidx/input/motionprediction/kalman/MultiPointerPredictor.java
@@ -161,7 +161,9 @@
 
         if (foundNullPrediction) {
             for (MotionEvent ev : singlePointerEvents) {
-                ev.recycle();
+                if (ev != null) {
+                    ev.recycle();
+                }
             }
             return null;
         }