[gtksourceview] vim: ensure ctrl+shift+u is available for unicode

[Christian Hergert <chergert src gnome org>]

commit 72098a9d5a6ab6ec7519a550dff6219fe031e0c0
Author: Christian Hergert <chergert redhat com>
Date:   Sun Dec 19 11:27:15 2021 -0800

    vim: ensure ctrl+shift+u is available for unicode
    
    Fixes https://gitlab.gnome.org/GNOME/gnome-text-editor/-/issues/260

 gtksourceview/vim/gtksourceviminsert.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/gtksourceview/vim/gtksourceviminsert.c b/gtksourceview/vim/gtksourceviminsert.c
index 57c4cf31..c9d2719e 100644
--- a/gtksourceview/vim/gtksourceviminsert.c
+++ b/gtksourceview/vim/gtksourceviminsert.c
@@ -118,7 +118,9 @@ gtk_source_vim_insert_handle_keypress (GtkSourceVimState *state,
                switch (keyval)
                {
                        case GDK_KEY_u:
-                               return clear_to_first_char (self);
+                               if ((mods & GDK_SHIFT_MASK) == 0)
+                                       return clear_to_first_char (self);
+                               break;
 
                        case GDK_KEY_v:
                                gtk_source_vim_state_push (state, gtk_source_vim_insert_literal_new ());