Snapshot fix, Post-Processing was ignored in snapshots

git-svn-id: http://www.openflipper.org/svnrepo/OpenFlipper/branches/Free@17797 383ad7c9-94d9-4d36-a494-682f7c89f535

Shaders/Sobel/sobel.glsl

@@ -31,4 +31,5 @@ void main()
        color_vertical   += abs(texture2D(textureSampler, coord_tr)      - texture2D(textureSampler, coord_br));     
        
   oColor = color_horizontal + color_vertical;
+  oColor.a = 1.0;
 }