patch 9.0.0272: BufReadCmd not triggered when loading a "nofile" buffer

Problem:    BufReadCmd not triggered when loading a "nofile" buffer. (Maxim
            Kim)
Solution:   Call readfile() but bail out before reading a file.
            (closes #10983)
diff --git a/src/fileio.c b/src/fileio.c
index 6d063a5..1b30e0f 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -108,6 +108,7 @@
  * READ_STDIN	read from stdin instead of a file
  * READ_BUFFER	read from curbuf instead of a file (converting after reading
  *		stdin)
+ * READ_NOFILE	do not read a file, only trigger BufReadCmd
  * READ_DUMMY	read into a dummy buffer (to check if file contents changed)
  * READ_KEEP_UNDO  don't clear undo info or read it from a file
  * READ_FIFO	read from fifo/socket instead of a file
@@ -309,6 +310,9 @@
 #endif
 
 	curbuf->b_op_start = orig_start;
+
+	if (flags & READ_NOFILE)
+	    return FAIL;
     }
 
     if ((shortmess(SHM_OVER) || curbuf->b_help) && p_verbose == 0)