[gimp] fix NaN issue in gimpoperationlevels.c

[Simon Budig <simon src gnome org>]

commit 8482fb9cf65c11f6fbef85ae84be9cab804bd444
Author: Simon Budig <simon budig de>
Date:   Wed May 9 02:24:12 2012 +0200

    fix NaN issue in gimpoperationlevels.c

 app/gegl/gimpoperationlevels.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/app/gegl/gimpoperationlevels.c b/app/gegl/gimpoperationlevels.c
index f36f3e77..7bd25f9 100644
--- a/app/gegl/gimpoperationlevels.c
+++ b/app/gegl/gimpoperationlevels.c
@@ -86,6 +86,9 @@ gimp_operation_levels_map (gdouble value,
                            gdouble low_output,
                            gdouble high_output)
 {
+  /* clamp to guard pow() against negative input */
+  value = MAX (value, low_input);
+
   /*  determine input intensity  */
   if (high_input != low_input)
     value = (value - low_input) / (high_input - low_input);