fix: Type check for snippet description #1832

[Forsigg]

Add type check for item.detail that contains description, In that case while navigating in menu for select snippet item.detail contains table, but expected string

#1832

[ghost]

@hrsh7th, can you please merge this as quickly as possible? I got the same error as him(#1832). When I added the codes that he wrote into my local nvim cmp codes, it worked without making any errors. Please check it and merge it. @Forsigg THank you!

[hrsh7th]

IMO, the item.detail as table is not compliant fir LSP spec. So I tgink it should be fixed in source side.

[rbjorklin]

I also just hit this and the commit in this PR works as a work-around.

@hrsh7th What is the "source side" in this scenario? Should this bug be reported against another project? If so, which one?

[Shougo]

@hrsh7th What is the "source side" in this scenario? Should this bug be reported against another project? If so, which one?

If it is source side problem, the source should check the item.detail instead.