Filter higherrank results if not allowed

[willgearty]

In some cases (see "Leptotyphlops conjunctus"), the first result from get_gbifid_ is a "HIGHERRANK" match, even when there are also exact matches. Currently the function doesn't filter out this match, and if it has an "ACCEPTED" status, it'll be selected by the function, but then filtered out later, resulting in "No matching species concept!" even though there may have been species matches. This filters out the "HIGHERRANK" matches beforehand if higherrank = TRUE to prevent this.

I also added some additional checks in the if loops to make sure there are still matches before we check them for various things.