fix parsing ranges for num field in form dialog

src/form.c

@@ -207,7 +207,7 @@ set_field_value (guint num, gchar * value)
           if (s[1])
             {
               gchar **s1 = g_strsplit (s[1], "..", 2);
-              if (s[0] && s[1])
+              if (s1[0] && s1[1])
                 {
                   gdouble min, max;
                   min = g_ascii_strtod (s1[0], NULL);