I'm afraid these threads always bring out the alarmists ...... Every glass tank I ever had has some bubbles in the silicone seams. OK, yes, it could fail tomorrow; but it could also last for another decade. No way to know definitively. If it were my tank, I'd just monitor the bubbles. If they get larger over time, THEN you have a problem. Assume this tank was new when you got it. My standard position is to never buy a large used tank ..... never.
BTW, you are correct that on a DiY stand, any warranty is void so hopefully it was made well. I think bad stands are more responsible for large tank failures than everything else.