[babl] cairo: pad with 255 instead of copy of color for 24bit format

[Øyvind Kolås <ok src gnome org>]

commit 386a7d3eed347da604ddbee91940399a68eb13fc
Author: Øyvind Kolås <pippin gimp org>
Date:   Wed Nov 16 23:52:26 2016 +0100

    cairo: pad with 255 instead of copy of color for 24bit format

 extensions/cairo.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/extensions/cairo.c b/extensions/cairo.c
index 7ebf333..2714557 100644
--- a/extensions/cairo.c
+++ b/extensions/cairo.c
@@ -33,7 +33,7 @@ conv_rgba8_cairo24_le (unsigned char *src, unsigned char *dst, long samples)
       dst[0] = src[2];
       dst[1] = src[1];
       dst[2] = src[0];
-      dst[3] = src[0];
+      dst[3] = 255;
       src+=4;
       dst+=4;
     }
@@ -49,7 +49,7 @@ conv_rgb8_cairo24_le (unsigned char *src, unsigned char *dst, long samples)
       dst[0] = src[2];
       dst[1] = src[1];
       dst[2] = src[0];
-      dst[3] = src[0];
+      dst[3] = 255;
       src+=3;
       dst+=4;
     }