Add null check before updating animation progress

Haven't been able to reproduce it locally, but seems theoretically
possible if we get an onDrag() event right after something else
cancels the animation (which clears the animation controller).

Bug: 157900227
Change-Id: Ia134aa948e62d39f71e41dd4e6b98f3227ae0522

src/com/android/launcher3/touch/AbstractStateChangeTouchController.java

@@ -310,6 +310,9 @@ public abstract class AbstractStateChangeTouchController
     }
 
     protected void updateProgress(float fraction) {
+        if (mCurrentAnimation == null) {
+            return;
+        }
         mCurrentAnimation.setPlayFraction(fraction);
         if (mAtomicComponentsController != null) {
             // Make sure we don't divide by 0, and have at least a small runway.