patch 8.2.2489: current buffer is wrong after deletebufline() fails

Problem:    current buffer is wrong after deletebufline() fails to delete a
            line in another buffer.
Solution:   Restore the current buffer.

src/evalbuffer.c

@@ -500,9 +500,9 @@ f_deletebufline(typval_T *argvars, typval_T *rettv)
     if (u_save(first - 1, last + 1) == FAIL)
     {
 	rettv->vval.v_number = 1;	// FAIL
-	return;
     }
-
+    else
+    {
 	for (lnum = first; lnum <= last; ++lnum)
 	    ml_delete_flags(first, ML_DEL_MESSAGE);
 
@@ -518,6 +518,7 @@ f_deletebufline(typval_T *argvars, typval_T *rettv)
 	    }
 	check_cursor_col();
 	deleted_lines_mark(first, count);
+    }
 
     if (!is_curbuf)
     {

src/testdir/test_bufline.vim

@@ -186,6 +186,17 @@ func Test_deletebufline()
   call assert_equal(0, deletebufline(b, 1))
   call assert_equal(['b', 'c'], getbufline(b, 1, 2))
   exe "bwipe! " . b
+
+  edit XbufOne
+  let one = bufnr()
+  call setline(1, ['a', 'b', 'c'])
+  setlocal nomodifiable
+  split XbufTwo
+  let two = bufnr()
+  call assert_fails('call deletebufline(one, 1)', 'E21:')
+  call assert_equal(two, bufnr())
+  bwipe! XbufTwo
+  bwipe! XbufOne
 endfunc
 
 func Test_appendbufline_redraw()

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2489,
 /**/
     2488,
 /**/