Fix firing event inside class causing internal error

[wsnyder]

Firing an event inside a class method caused a fault.

class Cls;
  event e;
  task trig_e();
    ->> e;
  endtask
endclass

The next commit will include a test (still failing), with a new assertion that fails instead of a segfault. We need to fix to avoid the assertion.

Maybe @gezalore or @kozdra if you have a chance to look at it?