Fix disappearing of server browser search input

[lopezloo]

This is a test fix for #2644. Hard to say if it really work because it's random and quite rare bug.

There is some logic which makes search input flash after player type something in it, close server browser and then open it again to give signal to player that server list is being filtered: https://github.com/multitheftauto/mtasa-blue/blob/16769b8d1c94e2b9fe6323dcba46d1305f87a190/Client/core/ServerBrowser/CServerBrowser.cpp#L704-L712

Stuff in m_FlashSearchBox is not being cleared after closing server browser while CServerBrowser::Update() is being called even if server browser is closed so I think it might be race condition.