[gegl] tests: fix missing string format argument

[Michael Natterer <mitch src gnome org>]

commit c5c78182d83ed799ab87a0a55eae94f8a734996c
Author: Tim Lunn <tim feathertop org>
Date:   Mon Mar 30 08:19:19 2015 +1100

    tests: fix missing string format argument
    
    This causes a build failure when building with -Werror=format-security
    
    https://bugzilla.gnome.org/show_bug.cgi?id=746984

 tests/simple/test-gegl-color.c |    8 ++------
 1 files changed, 2 insertions(+), 6 deletions(-)
---
diff --git a/tests/simple/test-gegl-color.c b/tests/simple/test-gegl-color.c
index 4c5bdbe..ce00574 100644
--- a/tests/simple/test-gegl-color.c
+++ b/tests/simple/test-gegl-color.c
@@ -40,14 +40,10 @@ assert_compare_rgba(const gdouble actual[4], const gdouble expect[4])
     }
 
     if (!colors_equal) {
-        gchar str[100];
-        g_snprintf(str, 100,
-                "GeglColor("COLOR_FMT","COLOR_FMT","COLOR_FMT","COLOR_FMT") != " \
+        g_error("GeglColor("COLOR_FMT","COLOR_FMT","COLOR_FMT","COLOR_FMT") != "
                 "GeglColor("COLOR_FMT","COLOR_FMT","COLOR_FMT","COLOR_FMT")",
                 actual[0], actual[1], actual[2], actual[3],
-                expect[0], expect[1], expect[2], expect[3]
-        );
-        g_error(str);
+                expect[0], expect[1], expect[2], expect[3]);
     }
     g_assert(colors_equal);
 }