patch 8.2.1611: Vim9: cannot pass "true" to nr2char()

Problem:    Vim9: cannot pass "true" to nr2char().
Solution:   use tv_get_bool_chk(). (closes #6878)

Author: brammool

src/evalfunc.c

@@ -5874,7 +5874,7 @@ f_nr2char(typval_T *argvars, typval_T *rettv)
 	int	utf8 = 0;
 
 	if (argvars[1].v_type != VAR_UNKNOWN)
-	    utf8 = (int)tv_get_number_chk(&argvars[1], NULL);
+	    utf8 = (int)tv_get_bool_chk(&argvars[1], NULL);
 	if (utf8)
 	    buf[utf_char2bytes((int)tv_get_number(&argvars[0]), buf)] = NUL;
 	else

src/testdir/test_vim9_func.vim

@@ -1529,6 +1529,10 @@ def Test_list2str_str2list_utf8()
   assert_equal(s, list2str(l, true))
 enddef
 
+def Test_nr2char()
+  assert_equal('a', nr2char(97, true))
+enddef
+
 def Fibonacci(n: number): number
   if n < 2
     return n

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1611,
 /**/
     1610,
 /**/