[mutter/wip/carlosg/null-preedit] wayland: Handle NULL preedit text

[Carlos Garnacho <carlosg src gnome org>]

commit c98902701356e0d0746bc40a1095f9001e8404c1
Author: Carlos Garnacho <carlosg gnome org>
Date:   Tue Mar 24 16:52:55 2020 +0100

    wayland: Handle NULL preedit text
    
    The preedit text may be NULL (eg. when unsetting it). This started
    causing crashes since commit db9b60cc635, duh.
    
    Fixes: https://gitlab.gnome.org/GNOME/mutter/-/issues/1132

 src/wayland/meta-wayland-text-input.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/src/wayland/meta-wayland-text-input.c b/src/wayland/meta-wayland-text-input.c
index deff44c1b..4e7d18b25 100644
--- a/src/wayland/meta-wayland-text-input.c
+++ b/src/wayland/meta-wayland-text-input.c
@@ -207,10 +207,12 @@ meta_wayland_text_input_focus_set_preedit_text (ClutterInputFocus *focus,
 {
   MetaWaylandTextInput *text_input;
   struct wl_resource *resource;
-  gsize pos;
+  gsize pos = 0;
 
   text_input = META_WAYLAND_TEXT_INPUT_FOCUS (focus)->text_input;
-  pos = g_utf8_offset_to_pointer (text, cursor) - text;
+
+  if (text)
+    pos = g_utf8_offset_to_pointer (text, cursor) - text;
 
   wl_resource_for_each (resource, &text_input->focus_resource_list)
     {