The glue being discussed here is referred to as automotive seam sealer. It is used to seal gaps between the multiple sheets of stamped steel that are modern cars 'frames' [unibody] are comprised from water intrusion, wind and noise. Not every gap requires the seam sealer and it is not structural. Furthermore the multiple pieces of stamped steel are spot welded (resistance welded) together not continuous 'beads' of weld (filler welding) so there are gaps like this all over that are completely normal but covered over with seam sealer to prevent water from getting trapped in the gaps. That area of the shock tower is multiple layers of stamped steel, if it were coming apart or structurally compromised you would know it as this thread would be about very alarming noises and or vehicle behavior and not just about a gap in seam sealer.
In short, just add some seam sealer. If it gets worse and you start hearing noises and the vehicle behaves abnormally then you have a problem. It looks like it could have just been applied a little too thin there, or something has recently happened with this vehicle.