Go slightly larger during initial scaling in PlaylistEntryImage

There are some cases where the scaled image would still be one
pixel less than desired in height or width, so go slightly larger
to ensure we can crop down to the desired size for display.

src/playlist/PlaylistEntryImage.cpp

@@ -292,7 +292,7 @@ void PlaylistEntryImage::PrepImage(void) {
             // Resize to slightly larger since trying to get exact can
             // leave us off by one pixel.  Going slightly larger will let
             // us crop to exact size later.
-            image.resize(Geometry(m_width + 2, m_height + 2, 0, 0));
+            image.resize(Geometry(m_width + 4, m_height + 4, 0, 0));
 
             cols = image.columns();
             rows = image.rows();