That looks like a minor casting flaw to me, rather than a crack. Not of concern, if it doesn't leak gas to the outside.
You can probably pick up a 'fixer-upper' edger for not much coin, via FleaBay or Dumbtree.
The Victa Tilt-a-cut 2-stroke models are common, well built, and very repairable, if you don't mind the noise! They also do an excellent job, when fitted with the circular blade that the later models used.
