Fix custom cursors on Mac. Null and 0 turn out not to be opposites....

webkit/glue/webcursor_mac.mm

Index: webkit/glue/webcursor_mac.mm
===================================================================
--- webkit/glue/webcursor_mac.mm	(revision 20280)
+++ webkit/glue/webcursor_mac.mm	(working copy)
@@ -49,6 +49,8 @@
 NSCursor* CreateCustomCursor(const std::vector<char>& custom_data,
                              const gfx::Size& custom_size,
                              const gfx::Point& hotspot) {
+  DCHECK(!custom_data.empty());

[pink (ping after 24hrs), 2009/07/09 21:30:31]

is it worth being over-protective (since this takes out the browser process
hard) and returning nil if this check fails? Can callers handle that? Is it
better than throwing a cocoa exception here in release builds?

[darin (slow to review), 2009/07/09 21:35:45]

we should only reach here if webkit tries to send us a custom cursor that has no
data.  that situation shouldn't be possible.

will our crash handler catch the cocoa exception?

return early just gimps the feature silently.  i'd much rather get a crash
report.

+
   scoped_cftyperef<CGImageRef> cg_image(
       CreateCGImageFromCustomData(custom_data, custom_size));