Hand Ball in box penalty shot vs Goal awarded

[Nevadaref]

Coach,
I don't work indoor soccer, but I can give you a ruling on your play for outdoor FIFA.
Since you said that the handball was unintentional, it is NOT a foul at all. Play should not be stopped and the goal counts.
Now if we change the play a bit, we make it harder, but more instructive. Let's say the restart is an indirect free kick and that the defender does intentionally handle the ball in the area, but it goes into the goal anyway.
The Law tells us that this is a foul, but it is not a red card since a goal was not denied by the handling. The fact that it was an IFK (similar to your indoor restart) means that the foul cannot deny a goal since one cannot legally be scored directly from the kick.
The proper thing for the official to do is the wait until the ball either enters the goal or it is clear that it won't until he blows the whistle. Blowing it before would nullify an otherwise deserved goal due to the ball now being out of play.
By waiting, advantage can be applied to this situation and the attackers properly awarded a goal. The defender should still be cautioned for the handling offense.