vim-patch:7.4.1834 (#5854)

Problem:    Possible crash when conceal is active.
Solution:   Check for the screen to be valid when redrawing a line.

908be43879

src/nvim/version.c

@@ -606,6 +606,7 @@ static int included_patches[] = {
   1837,
   1836,
   1835,
+  1834,
   1833,
   1832,
   1831,