Pass the correct number of arguments to preview
Pass the correct number of arguments to preview

Fix "E119: Not enough arguments for function:
<SNR>326_CBPreviewDefinition" when doing `:OmniSharpPreviewDefinition`.

In 5813d6a0, more arguments were added to CBPreviewDefinition, but they
were only added in the OmniSharp_server_stdio call site.

Add empty dicts to the second callsite to provide the required number of
arguments.

OmniSharp/omnisharp-vim,OmniSharp/omnisharp-vim,OmniSharp/omnisharp-vim