vim-patch:9.0.1233: search() loops forever if "skip" is TRUE for all matches (#21956)

Problem:    search() loops forever if "skip" is TRUE for all matches.
Solution:   Keep the position of the first match.

3d79f0a430

Co-authored-by: Bram Moolenaar <Bram@vim.org>

src/nvim/eval/funcs.c

@@ -6239,7 +6239,9 @@ static int search_cmn(typval_T *argvars, pos_T *match_pos, int *flagsp)
       // didn't find it or no skip argument
       break;
     }
-    firstpos = pos;
+    if (firstpos.lnum == 0) {
+      firstpos = pos;
+    }
 
     // If the skip expression matches, ignore this match.
     {