I think the intended behavior is for you to solve the error before writing the javadoc any further. If you want to a quick way to get around it, you can bring up the javadoc via the shortcuts:
Fn + Shift + F2
Shift + F2
Edit: basin kindly pointed out that the javadoc needs to be attached. You should be able to see the javadoc of a class having attached source in eclipse by:
select Window -> show view -> javadoc (or alt + shift + q, j).
then in the javadoc view, right click -> open attached javadoc (or shift + F2), this will display the javadoc of the class in the internal browser of eclipse.