`lsp-ui-peek -find-workspace-symbol ` not working

[lebensterben]

I'm using Spacemacs and I found lsp-ui-peek-find-workspace-symbol not working in rust-mode for both rls and rust-analyzer backend.

I haven't tried other major modes but I think this bug is not caused by a particular backend, because both lsp-ui-find-workspace-symbol and helm-lsp-workspace-symbol are working, so certainly the backend can correctly responds to workspace/symbol requests.