When running as a wayland compositor, MetaCursorTracker might
legitimately not have a displayed cursor because e.g. a client unsets
the cursor surface.
Note that, under an X session, the assumption that the tracker always
has a cursor texture is true because XFixesGetCursorImage() always
returns data even if the cursor isn't visible.
https://bugzilla.gnome.org/show_bug.cgi?id=767001
guint8 *data;
texture = meta_cursor_tracker_get_sprite (recorder->cursor_tracker);
+ if (!texture)
+ return;
+
width = cogl_texture_get_width (texture);
height = cogl_texture_get_height (texture);
stride = 4 * width;