Fix earlier change to content URI resolution on Android

* java/org/gnu/emacs/EmacsService.java (openContentUri): Return
-1 if fd be NULL.

* src/androidvfs.c (android_authority_open): Detect
SecurityException and suchlike.
(android_vfs_init): Initialize exception classes on Android 4.4.

java/org/gnu/emacs/EmacsService.java

@@ -968,7 +968,7 @@ public final class EmacsService extends Service
      string; make it writable if WRITABLE, and readable if READABLE.
      Truncate the file if TRUNCATE.
 
-     Value is the resulting file descriptor or an exception will be
+     Value is the resulting file descriptor, -1, or an exception will be
      raised.  */
 
   public int
@@ -999,6 +999,9 @@ public final class EmacsService extends Service
        minimum requirement for access to /content/by-authority.  */
 
     fd = resolver.openFileDescriptor (Uri.parse (uri), mode);
+    if (fd == null)
+      return -1;
+
     i = fd.detachFd ();
     fd.close ();