Avoid crash with None tasks

[ssbarnea]

As ansible allows tasks to be None, we should also avoid crashing when
encountering them.

Includes regression prevention by assuring we can parse files
with empty tasks.

Fixes: #468

[rafaelfolco]

empty name with no action would be a good test case, isn't it?

[greg-hellings]

The if foo in (bar or []): is weird syntax to my eyes. Took me a minute to get what it's doing, I've just never seen it used like this in Python before. Once I got my eyes wrapped around it, this looks good.

[ssbarnea]

The if foo in (bar or []): is weird syntax to my eyes. Took me a minute to get what it's doing, I've just never seen it used like this in Python before. Once I got my eyes wrapped around it, this looks good.

Yes is weird, probably if bar and foo in bar would look better? Even so they both serve the same purpose.

I guess you need a better python knowledge to know that "False or []" returns [] and not False (but is evaluated as False if needed).

[greg-hellings]

The if foo in (bar or []): is weird syntax to my eyes. Took me a minute to get what it's doing, I've just never seen it used like this in Python before. Once I got my eyes wrapped around it, this looks good.

Yes is weird, probably if bar and foo in bar would look better? Even so they both serve the same purpose.

I guess you need a better python knowledge to know that "False or []" returns [] and not False (but is evaluated as False if needed).

Yes, I've seen it used in assignment and short-hand execution but hadn't seen it used in a conditional before. I agree that this form is the more commonly encountered conditional guard from my experience.

[greg-hellings]

lgtm

[albinvass]

lgtm