[UX] Do not allow to close global filter if there is a value

[zaverden]

Problem

At the moment it is possible to have global filter closed even if it's not empty. this is not a good user experience. for example, if I have global filter from query string and send tht link to mates - they'll see filtered data but will be unaware there is a filter. only if developer did not forget to set initialState.showGlobalFilter based on query

Proposal

Do not allow to close global filter if there is a value (have it always open)

I implement it if this proposal feels reasonable

[KevinVandy]

Good idea. So disable the toggle button when a filter is present, or clear the global filter when the search box is hidden?

[KevinVandy]

The toggle search button is now disabled when a global filter is present as of beta.9