[gimp] app: in gimp-spawn.c, add missing #include on Windows

[N/A <ell src gnome org>]

commit 52b0e610017e46a35771a048ee0cec5255d4abca
Author: Ell <ell_se yahoo com>
Date:   Wed Mar 7 01:40:10 2018 -0500

    app: in gimp-spawn.c, add missing #include on Windows
    
    ... and improve argument validation.

 app/core/gimp-spawn.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/app/core/gimp-spawn.c b/app/core/gimp-spawn.c
index 071b135..b86a2a2 100644
--- a/app/core/gimp-spawn.c
+++ b/app/core/gimp-spawn.c
@@ -33,6 +33,7 @@
 
 #ifdef G_OS_WIN32
 #include <windows.h>
+#include <io.h>
 #endif
 
 #include <glib-object.h>
@@ -164,6 +165,7 @@ gimp_spawn_async (gchar       **argv,
                   GError      **error)
 {
   g_return_val_if_fail (argv != NULL, FALSE);
+  g_return_val_if_fail (argv[0] != NULL, FALSE);
 
 #ifdef HAVE_VFORK
   if (flags == (G_SPAWN_LEAVE_DESCRIPTORS_OPEN |