[PATCH] ole32: Add parameter check for clipbrd_wndproc

[Zhipeng Zhao]

After debug a bit more, I see clipbrd->cached_enum is NULL not clipbrd.<br/>When using Ctrl + x to cut the picture in the wechat-work input box, and then switch another chat window, this time the crash appears.<br/><br/>Thanks,<br/>Zhipeng.
At 2020-04-03 17:53:06, "Huw Davies" <huw at codeweavers.com> wrote:
>On Fri, Mar 27, 2020 at 01:26:06PM +0800, Zhipeng Zhao wrote:
>> When I use wechat-work to do some clip, there raise a exception.
>> 
>> Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=48826
>> Signed-off-by: Zhipeng Zhao <near2see at 163.com>
>> ---
>>  dlls/ole32/clipboard.c | 5 +++++
>>  1 file changed, 5 insertions(+)
>> 
>> diff --git a/dlls/ole32/clipboard.c b/dlls/ole32/clipboard.c
>> index 9df37750a3..69a8fc61b2 100644
>> --- a/dlls/ole32/clipboard.c
>> +++ b/dlls/ole32/clipboard.c
>> @@ -2066,6 +2066,11 @@ static LRESULT CALLBACK clipbrd_wndproc(HWND hwnd, UINT message, WPARAM wparam,
>>          ole_priv_data_entry *entry;
>>  
>>          TRACE("(): WM_RENDERFORMAT(cfFormat=%x)\n", cf);
>> +        if (!clipbrd || !clipbrd->cached_enum)
>> +        {
>> +            entry = NULL;
>> +            break;
>> +        } 
>>          entry = find_format_in_list(clipbrd->cached_enum->entries, clipbrd->cached_enum->count, cf);
>>  
>>          if(entry)
>
>Could you debug this a bit further?  Is clipbrd or
>clipbrd->cached_enum NULL?  How does it get to this
>state?
>
>Thanks,
>Huw.