Fix NPE in processNestedScroll

Null check mCapturedView.

Bug:18114408
Change-Id: I5abb9f5bcca37aafab55f12c69d824ab92faf68f
diff --git a/src/com/android/dialer/widget/ViewDragHelper.java b/src/com/android/dialer/widget/ViewDragHelper.java
index a0e1d80..c0bc2ce 100644
--- a/src/com/android/dialer/widget/ViewDragHelper.java
+++ b/src/com/android/dialer/widget/ViewDragHelper.java
@@ -1548,6 +1548,12 @@
      *         deltas that it consumed.
      */
     public void processNestedScroll(View target, int dx, int dy, int[] consumed) {
+        if (mCapturedView == null) {
+            // This is safe because consumed array is null when called from
+            // onNestedScroll, and pre-initialized to {0, 0} when called from
+            // onNestedPreScroll.
+            return;
+        }
         final int targetX = mCapturedView.getLeft() + dx;
         final int targetY = mCapturedView.getTop() + dy;
         dragTo(targetX, targetY, dx, dy);