[babl] babl: further nan prevention in babl-trc

[Øyvind Kolås <ok src gnome org>]

commit e747cd9a21b2dcdca37d8dfc21a9c5d47767a89a
Author: Øyvind Kolås <pippin gimp org>
Date:   Mon Sep 11 00:41:47 2017 +0200

    babl: further nan prevention in babl-trc

 babl/babl-trc.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)
---
diff --git a/babl/babl-trc.c b/babl/babl-trc.c
index 6f97d83..7fa79f1 100644
--- a/babl/babl-trc.c
+++ b/babl/babl-trc.c
@@ -417,9 +417,13 @@ static inline float _babl_trc_formula_srgb_from_linear (const Babl *trc_, float
   {
     float v = babl_powf (x, 1.0/g);
     v = (v-b)/a;
-    return v;
+    if (v < 0.0 || v >= 0.0)
+      return v;
+    return 0.0;
   }
-  return x / c;
+  if (c > 0.0)
+    return x / c;
+  return 0.0;
 }
 
 static inline float _babl_trc_formula_srgb_to_linear (const Babl *trc_, float value)