patch 8.0.0703: illegal memory access with empty :doau command

Problem:    Illegal memory access with empty :doau command.
Solution:   Check the event for being out of range. (James McCoy)

src/fileio.c

@@ -8863,7 +8863,7 @@ do_doautocmd(
     /*
      * Loop over the events.
      */
-    while (*arg && !VIM_ISWHITE(*arg))
+    while (*arg && !ends_excmd(*arg) && !VIM_ISWHITE(*arg))
 	if (apply_autocmds_group(event_name2nr(arg, &arg),
 				      fname, NULL, TRUE, group, curbuf, NULL))
 	    nothing_done = FALSE;
@@ -9385,7 +9385,8 @@ apply_autocmds_group(
      * Quickly return if there are no autocommands for this event or
      * autocommands are blocked.
      */
-    if (first_autopat[(int)event] == NULL || autocmd_blocked > 0)
+    if (event == NUM_EVENTS || first_autopat[(int)event] == NULL
+	    || autocmd_blocked > 0)
 	goto BYPASS_AU;
 
     /*
@@ -9458,7 +9459,7 @@ apply_autocmds_group(
     {
 	if (event == EVENT_COLORSCHEME || event == EVENT_OPTIONSET)
 	    autocmd_fname = NULL;
-	else if (fname != NULL && *fname != NUL)
+	else if (fname != NULL && !ends_excmd(*fname))
 	    autocmd_fname = fname;
 	else if (buf != NULL)
 	    autocmd_fname = buf->b_ffname;

src/testdir/test_autocmd.vim

@@ -418,3 +418,7 @@ function Test_autocmd_bufwipe_in_SessLoadPost2()
     call delete(file)
   endfor
 endfunc
+
+func Test_empty_doau()
+  doau \|
+endfunc

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    703,
 /**/
     702,
 /**/