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/screen.c

@@ -486,6 +486,11 @@ void update_single_line(win_T *wp, linenr_T lnum)
   int row;
   int j;
 
+  // Don't do anything if the screen structures are (not yet) valid.
+  if (!screen_valid(true)) {
+    return;
+  }
+
   if (lnum >= wp->w_topline && lnum < wp->w_botline
       && foldedCount(wp, lnum, &win_foldinfo) == 0) {
     row = 0;

src/nvim/version.c

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