Quit monkeying around when it comes to the feelings and hearts of your lovers, experts say. Everyone knows at least one person in their life who’s never single — and swings from one beau to the next without missing a beat. Dating pros call it “monkey-barring” or “monkey-branching” — which is the act of clinging to one partner while lining up another behind your current flame’s back.  Too terrified of ever flying solo, these serial daters stick with one partner, only until the next is within reach.  But don’t confuse it with Gen Z’s trendy polyamory — that’s consensual and…