[evolution] Remove CSS sheet from the DOM only when it exists

[Tomas Popela <tpopela src gnome org>]

commit e7de96dc370e4954991a9f80c25ab8d6f944d144
Author: Tomas Popela <tpopela redhat com>
Date:   Wed Aug 31 15:40:25 2016 +0200

    Remove CSS sheet from the DOM only when it exists

 .../web-extension/e-editor-dom-functions.c         |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/modules/webkit-editor/web-extension/e-editor-dom-functions.c 
b/modules/webkit-editor/web-extension/e-editor-dom-functions.c
index a8d34bb..e778849 100644
--- a/modules/webkit-editor/web-extension/e-editor-dom-functions.c
+++ b/modules/webkit-editor/web-extension/e-editor-dom-functions.c
@@ -1774,7 +1774,8 @@ e_editor_dom_remove_embedded_style_sheet (EEditorPage *editor_page)
        sheet = webkit_dom_document_get_element_by_id (
                document, "-x-evo-composer-sheet");
 
-       remove_node (WEBKIT_DOM_NODE (sheet));
+       if (sheet)
+               remove_node (WEBKIT_DOM_NODE (sheet));
 }
 
 static void