Unable to load BRs in SAF of FileSystemProvider

Files.listFiles() indicate if this abstract pathname does "not denote a directory"
It will returns null and cause "NullPointerException: Attempt to get length of null array"
in the queryChildDocuments()

Solution:
    Use FileUtils.listFilesOrEmpty(parent) and check parent.isDirectory() to avoid NPE

Bug: 111565816
Test: Manual, trigger bugreport
      rm -rf /data/user_de/0/com.android.shell/files/bugreports
      launch Files/Bugreport observe there should not happen exception

Change-Id: I9d0835d562af7cf3c9bdaeab52cf41e86e3a8f62

1 files changed, 6 insertions, 2 deletions

diff --git a/core/java/com/android/internal/content/FileSystemProvider.java b/core/java/com/android/internal/content/FileSystemProvider.java
index f89a9d990b76..0c6f832ff33a 100644
--- a/core/java/com/android/internal/content/FileSystemProvider.java
+++ b/core/java/com/android/internal/content/FileSystemProvider.java
@@ -374,8 +374,12 @@ public abstract class FileSystemProvider extends DocumentsProvider {
         final File parent = getFileForDocId(parentDocumentId);
         final MatrixCursor result = new DirectoryCursor(
                 resolveProjection(projection), parentDocumentId, parent);
-        for (File file : parent.listFiles()) {
-            includeFile(result, null, file);
+        if (parent.isDirectory()) {
+            for (File file : FileUtils.listFilesOrEmpty(parent)) {
+                includeFile(result, null, file);
+            }
+        } else {
+            Log.w(TAG, "parentDocumentId '" + parentDocumentId + "' is not Directory");
         }
         return result;
     }