vim-patch:7.4.251

Problem:  Crash when BufAdd autocommand wipes out the buffer.

Solution: Check for buffer to still be valid. Postpone freeing the
          buffer structure. (Hirohito Higashi)

https://code.google.com/p/vim/source/detail?r=29eb4c2a33ac701bfcd4d2e2bed7864eba876e0e

src/ex_cmds.c

@@ -2774,6 +2774,11 @@ do_ecmd (
       }
       buf = buflist_new(ffname, sfname, 0L,
           BLN_CURBUF | ((flags & ECMD_SET_HELP) ? 0 : BLN_LISTED));
+      // Autocmds may change curwin and curbuf.
+      if (oldwin != NULL) {
+        oldwin = curwin;
+      }
+      old_curbuf = curbuf;
     }
     if (buf == NULL)
       goto theend;