MediaProvider: Avoid null pointer exceptions inside getCompressedAlbu…

…mArt

Check if path is not null to avoid a java.lang.NullPointerException.
If path is null, the following exception stack trace will be thrown:

java.lang.NullPointerException: Attempt to invoke virtual method 'char[] java.lang.String.toCharArray()' on a null object reference
    at java.io.File.fixSlashes(File.java:185)
    at java.io.File.<init>(File.java:134)
    at com.android.providers.media.MediaProvider.getCompressedAlbumArt(MediaProvider.java:4846)
    at com.android.providers.media.MediaProvider.makeThumbInternal(MediaProvider.java:5015)
    at com.android.providers.media.MediaProvider.getThumb(MediaProvider.java:5011)
    at com.android.providers.media.MediaProvider.openFile(MediaProvider.java:4601)
    at android.content.ContentProvider.openAssetFile(ContentProvider.java:1334)
    at android.content.ContentProvider.openTypedAssetFile(ContentProvider.java:1514)
    at android.content.ContentProvider.openTypedAssetFile(ContentProvider.java:1580)
    at android.content.ContentProvider$Transport.openTypedAssetFile(ContentProvider.java:391)
    at android.content.ContentProviderNative.onTransact(ContentProviderNative.java:312)
    at android.os.Binder.execTransact(Binder.java:446)

Change-Id: Ie27605590db20e0e4e12095d32864a246cc25573

src/com/android/providers/media/MediaProvider.java

@@ -4840,6 +4840,9 @@ private static boolean isRootStorageDir(String artPath) {
     // Extract compressed image data from the audio file itself or, if that fails,
     // look for a file "AlbumArt.jpg" in the containing directory.
     private static byte[] getCompressedAlbumArt(Context context, String path) {
+        if (path == null)
+            return null;
+
         byte[] compressed = null;
 
         try {