Fix crash when refreshing timeouts.

Test: Tested on an archvie and internal storage.
Change-Id: I583ca77d0046ed05dbec3f9ea9f845c1be7bc2bd
(cherry picked from commit 3777a1bc0122b84e6078cf1faa402918ffdfd2b1)
diff --git a/src/com/android/documentsui/RefreshTask.java b/src/com/android/documentsui/RefreshTask.java
index 4692082..5cec517 100644
--- a/src/com/android/documentsui/RefreshTask.java
+++ b/src/com/android/documentsui/RefreshTask.java
@@ -106,12 +106,13 @@
     @Override
     public void finish(Boolean refreshSupported) {
         if (DEBUG) {
-            if (refreshSupported) {
+            // In case of timeout, refreshSupported is null.
+            if (Boolean.TRUE.equals(refreshSupported)) {
                 Log.v(TAG, "Provider supports refresh and has refreshed");
             } else {
                 Log.v(TAG, "Provider does not support refresh and did not refresh");
             }
         }
-        mCallback.accept(refreshSupported);
+        mCallback.accept(refreshSupported != null ? refreshSupported : Boolean.FALSE);
     }
 }