Contacts Picker: Fix crash when tab goes away.

Bug: 1001452, 860467
Change-Id: I0ee2354eda509e800fd0c80a66408de4b01c2536
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1789151
Auto-Submit: Finnur Thorarinsson <finnur@chromium.org>
Reviewed-by: Theresa  <twellington@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Commit-Queue: Finnur Thorarinsson <finnur@chromium.org>
Cr-Commit-Position: refs/heads/master@{#695015}

content/public/android/java/src/org/chromium/content/browser/ContactsDialogHost.java

@@ -84,6 +84,8 @@ public class ContactsDialogHost implements ContactsPickerListener {
     @Override
     public void onContactsPickerUserAction(@ContactsPickerAction int action, List<Contact> contacts,
             int percentageShared, int propertiesRequested) {
+        if (mNativeContactsProviderAndroid == 0) return;
+
         switch (action) {
             case ContactsPickerAction.CANCEL:
                 ContactsDialogHostJni.get().endContactsList(