[zenity] fix compilation when webkitgtk is not installed

[Arx Henrique Pereira da Cruz <arxcruz src gnome org>]

commit 61c53a042418562c30e816fdd0c63caf2fa9f1b3
Author: Tom Schoonjans <Tom Schoonjans diamond ac uk>
Date:   Sat Oct 17 17:52:44 2015 +0100

    fix compilation when webkitgtk is not installed

 src/option.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/src/option.c b/src/option.c
index 79a6f92..246cf22 100644
--- a/src/option.c
+++ b/src/option.c
@@ -2074,9 +2074,11 @@ zenity_text_post_callback (GOptionContext *context,
     if (zenity_text_font) 
       zenity_option_error (zenity_option_get_name (text_options, &zenity_text_font),
                            ERROR_SUPPORT);
+#ifdef HAVE_WEBKITGTK
     if (zenity_text_enable_html)
       zenity_option_error (zenity_option_get_name (text_options, &zenity_text_enable_html),
                            ERROR_SUPPORT);
+#endif
   }
   return TRUE;
 }