[babl] babl: make babl_model_is deal with NULL input

[Øyvind "pippin" Kolås <ok src gnome org>]

commit e62e0194a08c04d0125d7e725ea262f93110d49d
Author: Øyvind Kolås <pippin gimp org>
Date:   Sun Oct 28 03:08:30 2018 +0100

    babl: make babl_model_is deal with NULL input

 babl/babl.c | 2 +-
 babl/babl.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/babl/babl.c b/babl/babl.c
index 979cd46..4479f68 100644
--- a/babl/babl.c
+++ b/babl/babl.c
@@ -185,6 +185,6 @@ babl_exit (void)
 
 int babl_model_is (const Babl *babl, const char *model)
 {
-  return ((babl)==babl_model_with_space(model, babl));
+  return babl && ((babl)==babl_model_with_space(model, babl));
 }
 
diff --git a/babl/babl.h b/babl/babl.h
index 5a7ca7e..943de99 100644
--- a/babl/babl.h
+++ b/babl/babl.h
@@ -542,7 +542,7 @@ void babl_space_get (const Babl *space,
  */
 int babl_model_is (const Babl *babl, const char *model_name);
 
-#define babl_model_is(babl,model)  ((babl)==babl_model_with_space(model,babl))
+#define babl_model_is(babl,model)  (babl&&(babl)==babl_model_with_space(model,babl))
 
 
 /**