[gdk-pixbuf] io-ico: Add an assertion to clarify buffer management

[Philip Withnall <pwithnall src gnome org>]

commit 48accc7397d6802f3faa0fb9a4024babc980a09a
Author: Philip Withnall <withnall endlessm com>
Date:   Wed Feb 8 09:34:33 2017 +0000

    io-ico: Add an assertion to clarify buffer management
    
    The code is correct (the line buffer is set when DecodeHeader() returns
    successfully with a non-zero-length line), but that’s not at all obvious
    from the code, and is tripping Coverity up. Add an assertion to make it
    clearer.
    
    Coverity ID: 1400057
    
    https://bugzilla.gnome.org/show_bug.cgi?id=778943

 gdk-pixbuf/io-ico.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/gdk-pixbuf/io-ico.c b/gdk-pixbuf/io-ico.c
index 32e4c69..8729a0f 100644
--- a/gdk-pixbuf/io-ico.c
+++ b/gdk-pixbuf/io-ico.c
@@ -950,6 +950,9 @@ gdk_pixbuf__ico_image_load_increment(gpointer data,
                                BytesToCopy = size;
 
                        if (BytesToCopy > 0) {
+                               /* Should be non-NULL once the header is decoded, as below. */
+                               g_assert (context->LineBuf != NULL);
+
                                memmove(context->LineBuf +
                                       context->LineDone, buf,
                                       BytesToCopy);