[Paint Preview] Fix low-volume crash

This CL fixes a low-volume crash in paint preview code. Where the
tab might be null when checking if shown and needs badge.

This CL was uploaded by git cl split.

Change-Id: I69c03fb298c1d70b13368d6f9056d744231caee2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2401321
Commit-Queue: Mehran Mahmoudi <mahmoudi@chromium.org>
Reviewed-by: Mehran Mahmoudi <mahmoudi@chromium.org>
Auto-Submit: Calder Kitagawa <ckitagawa@chromium.org>
Cr-Commit-Position: refs/heads/master@{#805427}

chrome/browser/paint_preview/android/java/src/org/chromium/chrome/browser/paint_preview/TabbedPaintPreviewPlayer.java

@@ -234,6 +234,8 @@ public class TabbedPaintPreviewPlayer implements TabViewProvider, UserData {
     }
 
     public boolean isShowingAndNeedsBadge() {
+        if (mTab == null) return false;
+
         return mTab.getTabViewManager().isShowing(this);
     }