vim-patch:8.2.5013: after text formatting cursor may be in an invalid position

Problem:    After text formatting the cursor may be in an invalid position.
Solution:   Correct the cursor position after formatting.
78d52883e1

src/nvim/ops.c

@@ -4349,6 +4349,9 @@ static void op_format(oparg_T *oap, int keep_cursor)
   if (keep_cursor) {
     curwin->w_cursor = saved_cursor;
     saved_cursor.lnum = 0;
+
+    // formatting may have made the cursor position invalid
+    check_cursor();
   }
 
   if (oap->is_VIsual) {

src/nvim/testdir/test_textformat.vim

@@ -1534,4 +1534,16 @@ func Test_autoformat_comments()
   close!
 endfunc
 
+" This was leaving the cursor after the end of a line.  Complicated way to
+" have the problem show up with valgrind.
+func Test_correct_cursor_position()
+  " set encoding=iso8859
+  new
+  norm a000“0
+  sil! norm gggg0i0gw0gg
+
+  bwipe!
+  set encoding=utf8
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab