fix crash bug on black rectangle.

ByakuGallery/src/com/diegocarloslima/byakugallery/lib/TileBitmapDrawable.java

@@ -15,6 +15,7 @@
 import android.graphics.BitmapFactory;
 import android.graphics.BitmapRegionDecoder;
 import android.graphics.Canvas;
+import android.graphics.Color;
 import android.graphics.ColorFilter;
 import android.graphics.Matrix;
 import android.graphics.Paint;
@@ -448,7 +449,14 @@ public void run() {
 				synchronized(mDecoder) {
 					bitmap = mDecoder.decodeRegion(tile.mTileRect, options);
 				}
-
+
+				if (bitmap == null) { // this case is black rectangle.
+					bitmap = Bitmap.createBitmap(tile.mTileRect.right - tile.mTileRect.left, tile.mTileRect.bottom
+							- tile.mTileRect.top, Config.ARGB_8888);
+					Canvas c = new Canvas(bitmap);
+					c.drawColor(Color.BLACK);
+				}
+
 				synchronized(sBitmapCacheLock) {
 					sBitmapCache.put(tile.getKey(), bitmap);
 				}