accept label before assert

[Alcaro]

[01:53:02]  <Sir Walrus> !rb as2
ee: assert ee == $8000
[01:53:02]  <randombot999#8226> Errors occurred while assembling.
<input>:2: error: (Elabel_before_if): Labels are not allowed before "assert" commands. Suggestion: move the label to a separate line.
    in block: [ee: assert ee == $8000]
[01:53:04]  <Sir Walrus> !rb as2
ee: : assert ee == $8000
[01:53:04]  <randombot999#8226> (no output)

I can see some logic behind banning labels before if (they're hard to parse in if false), but assert doesn't need any particular parsing.