patch 8.1.0060: crash when autocommands delete the current buffer

Problem:    Crash when autocommands delete the current buffer. (Dominique
            Pelle)
Solution:   Check that autocommands don't change the buffer.

Author: brammool

src/quickfix.c

@@ -6272,8 +6272,16 @@ ex_cbuffer(exarg_T *eap)
 	    if (res >= 0)
 		qf_list_changed(qi, qi->qf_curlist);
 	    if (au_name != NULL)
+	    {
+		buf_T *curbuf_old = curbuf;
+
 		apply_autocmds(EVENT_QUICKFIXCMDPOST, au_name,
 						curbuf->b_fname, TRUE, curbuf);
+		if (curbuf != curbuf_old)
+		    // Autocommands changed buffer, don't jump now, "qi" may
+		    // be invalid.
+		    res = 0;
+	    }
 	    if (res > 0 && (eap->cmdidx == CMD_cbuffer ||
 						eap->cmdidx == CMD_lbuffer))
 		qf_jump(qi, 0, 0, eap->forceit);  /* display first error */

src/testdir/test_quickfix.vim

@@ -3350,3 +3350,15 @@ func Test_qftitle()
   call assert_equal('Errors', w:quickfix_title)
   cclose
 endfunc
+
+func Test_lbuffer_with_bwipe()
+  new
+  new
+  augroup nasty
+    au * * bwipe
+  augroup END
+  lbuffer
+  augroup nasty
+    au!
+  augroup END
+endfunc

src/version.c

@@ -761,6 +761,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    60,
 /**/
     59,
 /**/