[gegl] tools: exp_combine fix signedness warning

[Øyvind "pippin" Kolås <ok src gnome org>]

commit 7a2621bef85a6aa67dcb0e512d67edba5ee190b7
Author: Øyvind Kolås <pippin gimp org>
Date:   Mon Aug 12 17:03:32 2019 +0200

    tools: exp_combine fix signedness warning

 tools/exp_combine.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/tools/exp_combine.cpp b/tools/exp_combine.cpp
index e041295e8..62c24d1db 100644
--- a/tools/exp_combine.cpp
+++ b/tools/exp_combine.cpp
@@ -1,5 +1,5 @@
 
-#include <gegl.h> 
+#include <gegl.h>
 
 #include <cstdlib>
 #include <cstdio>
@@ -107,7 +107,7 @@ main (int    argc,
                                   "operation", "gegl:exp-combine",
                                   NULL);
 
-  for (cursor = ARG_PATH_0; cursor < argc; ++cursor)
+  for (cursor = ARG_PATH_0; cursor < unsigned(argc); ++cursor)
   for (cursor = ARG_PATH_0; cursor < unsigned(argc); ++cursor)
     {
       const gchar *input_path;