Double negation is typical for Ukrainian. You cannot omit не here. You can just remember "ніколи ... не ..." as a pair, because it is mostly used in this combination.
That's interesting ... I went the literal route and thought it meant "we have never not seen you there" ... in other words "we always see you there". So the double negative is reinforcing, rather than negating the first negative?
I would not call it reinforcing, because it is just the way to negate an adverb+verb phrase in Ukrainian: to negate the whole "thing" expressed by the adverb+verb phrase you negate both, the adverb and the verb. So "бачити колись" (to see once), becomes "не бачити ніколи" (to see never).