from your pic it doesn't look that bad....Im not sure of your skill level but it looks easily welded back and ride....Its a common thing Im afraid to say..but I see this on a lot of machines..
From what I see in your pic,I would unbolt that whole side.Then I would grind some of the weld down and try to tap it up some.It doesn't look like it moved to much at all.After that I would reweld it.Alot of these weld breaks are where the weld meets the tube.it called a fusion line.the weld is laid on fast and hot and the tube it still cold.causing a hardened area on the outside of the bead that cools fast and becomes hardened and brittle.When I weld tube like this I like to tack tack tack tack and heat up evenly then grind and hen lay another pass oer the already hot metal....
Now Im guessing your out of warranty and if you don't have the skills needed,or don't feel confident then take to weld shop to look at Cause this would be and easy fix.I also would take a grinder with a wire wheel and go around the others on that side.I would be surprised it that was all that cracked...