Crash on IAssistProposalWidget for clipboard history.

Crash on using clipboard history.
Reproducibility: ~90%.

Steps to reproduce:

• Use ctrl+c on several different code snippets (2 in my case);
• Press ctr+shift+v;
• Do not release these keys and press "arrow down" (↓) to select one of entries;
• If there is no crash use "arrow down" (↓) several times while ctr+shift+v are not released;
• If steel no crash release ctr+shift+v and try to reproduce again.

"About" tab, locals are in attach.

I could not upload core dump cuz there is limitation on file size (30mb) and with maximum winrar compression dump is about 100mb. If you will need core dump please let me know.