fix: getScope level overwritten by nested assertion blocks

[wilsonjord]

unittest {
  auto a = 1;
  a.shoud.equal(1);
  receive(2.seconds, (int m) { m.should.equal(1); });
}

Currently, if a.should.equal(1) is triggered, the receive block source alone is printed. This is due to the lambda-containing assertion overwriting the previous scope.

This PR fixes getScope behavior, essentially locking in on the scope of the initial assert.

[gedaiu]

thanks!