[gimp] app: fix gimp_g_value_get_memsize() with GStrv value.

[Jehan <jehanp src gnome org>]

commit 8c1414eb025b81406ea3aa36e88bddbcd69c016b
Author: Jehan <jehan girinstud io>
Date:   Tue May 24 15:54:08 2022 +0200

    app: fix gimp_g_value_get_memsize() with GStrv value.
    
    Since GStrv are NULL-terminated arrays, there is always one additional
    pointer (NULL).
    This is a detail, but still, wrong since commit 8eb7f6df9e9 which
    replaced GimpStringArray by GStrv usage.

 app/core/gimp-memsize.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/app/core/gimp-memsize.c b/app/core/gimp-memsize.c
index 1aee3538d6..2826bda6da 100644
--- a/app/core/gimp-memsize.c
+++ b/app/core/gimp-memsize.c
@@ -232,13 +232,13 @@ gimp_g_value_get_memsize (GValue *value)
         }
       else if (G_VALUE_HOLDS (value, G_TYPE_STRV))
         {
-          char **array = g_value_get_boxed (value);
+          gchar **array = g_value_get_boxed (value);
 
           if (array)
             {
               guint length = g_strv_length (array);
 
-              memsize += length * sizeof (gchar *);
+              memsize += (length + 1) * sizeof (gchar *);
               for (gint i = 0; i < length; i++)
                 memsize += gimp_string_get_memsize (array[i]);
             }