[babl] babl: in babl-trc.c, fix babl_powf()

[Øyvind Kolås <ok src gnome org>]

commit 88753797ee06b5d4958a7ccea22de8dba55032f6
Author: Ell <ell_se yahoo com>
Date:   Sun Sep 10 11:27:43 2017 -0400

    babl: in babl-trc.c, fix babl_powf()

 babl/babl-trc.c |    6 ++----
 1 files changed, 2 insertions(+), 4 deletions(-)
---
diff --git a/babl/babl-trc.c b/babl/babl-trc.c
index b7a9717..6f97d83 100644
--- a/babl/babl-trc.c
+++ b/babl/babl-trc.c
@@ -366,10 +366,8 @@ static inline float obabl_powf(float x, float y)
 
 static inline float babl_powf (float x, float y)
 {
-  float ret;
-  ret = expf (y * logf (x));
-  if (ret < 0.0 || ret < 0.0f)
-    return ret;
+  if (x > 0.0f)
+    return expf (y * logf (x));
   return 0.0f;
 }