box: fix a crash on unknown function option

`func_opts_reg` definition misses a `OPT_END` termintator item. This
leads to UB on iterating it. Particularly when `func_opts_reg` is used
as argument to `opts_decode` in `func_def_new_from_tuple`.

Closes #8463

NO_DOC=bugfix

changelogs/unreleased/gh-8463-crash-on-create-function

+## bugfix/box
+
+* Fixed a crash on unknown function option (gh-8463).

src/box/func_def.c

@@ -55,6 +55,7 @@ const struct func_opts func_opts_default = {
 const struct opt_def func_opts_reg[] = {
 	OPT_DEF("is_multikey", OPT_BOOL, struct func_opts, is_multikey),
 	OPT_DEF("takes_raw_args", OPT_BOOL, struct func_opts, takes_raw_args),
+	OPT_END,
 };
 
 struct func_def *

test/box-luatest/func_test.lua

@@ -120,3 +120,24 @@ g.test_gh_7822_vfunc_format = function()
         t.assert_equals(box.space._vfunc:format(), box.space._func:format())
     end)
 end
+
+-- Try to set unknown option using low level API to reach UB issue.
+g.test_gh_8463_unknown_option = function()
+    g.server:exec(function()
+        local t = require('luatest')
+
+        box.schema.func.create('foo_opt', {body = 'function() return end'})
+        local f = box.space._func.index.name:get('foo_opt')
+        f = f:totable()
+        f[16] = {foo = true}
+        t.assert_error_msg_equals(
+            "Wrong function options: unexpected option 'foo'",
+            box.space._func.replace, box.space._func, f)
+    end)
+end
+
+g.after_test('test_gh_8463_unknown_option', function()
+    g.server:exec(function()
+        box.schema.func.drop('foo_opt', {if_exists = true})
+    end)
+end)