patch 8.2.3234: crash when printing long string with Lua

Problem:    Crash when printing long string with Lua.
Solution:   Remove lua_pop(). (Martin Tournoij, closes #8648)

src/testdir/test_lua.vim

@@ -850,6 +850,24 @@ func Test_luafile_error()
   bwipe!
 endfunc
 
+" Test :luafile printing a long string
+func Test_luafile_print()
+  new Xlua_file
+  let lines =<< trim END
+      local data = ''
+      for i = 1, 130 do
+	data = data .. 'xxxxx asd as as dad sad sad xz cxz  czxcxzczxc ad ad asd asd asd asd asd'
+      end
+      print(data)
+  END
+  call setline(1, lines)
+  w
+  luafile %
+
+  call delete('Xlua_file')
+  bwipe!
+endfunc
+
 " Test for dealing with strings containing newlines and null character
 func Test_lua_string_with_newline()
   let x = execute('lua print("Hello\nWorld")')