[babl] bug #783704, Check db NULL to avoid segfault if babl not initiated,

[Øyvind Kolås <ok src gnome org>]

commit 25b29df94f2ac5aac35d1195608529e47ebad943
Author: Guiu Rocafort <neandertalspeople gmail com>
Date:   Tue Jun 13 09:21:29 2017 +0200

    bug #783704, Check db NULL to avoid segfault if babl not initiated,

 babl/babl-internal.h |   12 ++++++++++--
 1 files changed, 10 insertions(+), 2 deletions(-)
---
diff --git a/babl/babl-internal.h b/babl/babl-internal.h
index 228faa5..42262d6 100644
--- a/babl/babl-internal.h
+++ b/babl/babl-internal.h
@@ -265,14 +265,22 @@ BABL_CLASS_MINIMAL_IMPLEMENT(klass)                           \
 const Babl *                                                  \
 babl_##klass (const char *name)                               \
 {                                                             \
-  Babl *babl;                                                 \
+  Babl *babl = NULL;                                          \
                                                               \
   if (babl_hmpf_on_name_lookups)                              \
     {                                                         \
       babl_log ("%s(\"%s\"): hmpf!", G_STRFUNC, name);        \
     }                                                         \
-  babl = babl_db_exist_by_name (db, name);                    \
                                                               \
+  if( db != NULL )                                            \
+   {                                                          \
+     babl = babl_db_exist_by_name (db, name);                \
+   }                                                          \
+ else{                                                        \
+   babl_fatal("You must call babl_init() first");             \
+ }                                                           \
+                                                              \
+                                                             \
   if (!babl)                                                  \
     {                                                         \
       babl_fatal ("%s(\"%s\"): not found", G_STRFUNC, name);  \