[LinearProgressIndicator] Added null check in requestAnimatorAfterCurrentCycle for disjoint indeterminate animator.

PiperOrigin-RevId: 388962420

Author: pekingme

lib/java/com/google/android/material/progressindicator/LinearIndeterminateDisjointAnimatorDelegate.java

@@ -130,7 +130,9 @@ public void cancelAnimatorImmediately() {
   public void requestCancelAnimatorAfterCurrentCycle() {
     if (drawable.isVisible()) {
       animatorCompleteEndRequested = true;
-      animator.setRepeatCount(0);
+      if (animator != null) {
+        animator.setRepeatCount(0);
+      }
     } else {
       cancelAnimatorImmediately();
     }