Fix #4961 (halo animations sometimes freeze)

[DisherProject]

As this comment says, we are only redrawing haloes if anything else in the map is invalidating at least one hex.

halo_man_->unrender(invalidated_) actually invalidates the hexes covered by haloes which need to be updated, so i'm just moving the call outside the if-clause.

[stevecotton]

I'm not familiar with this code, but it looks like a minimal change on top of code that's already too complex.

However, it also looks like a change that increases the messiness of the code - moving a draws-to-screen call into a sets-invalidation-flags function. So overall I'm slightly against merging this.

[CelticMinstrel]

For some reason, #4961 doesn't seem to be linked from this PR (though at least the commit is), so this comment endeavours to fix that.

[DisherProject]

I'm not familiar with this code, but it looks like a minimal change on top of code that's already too complex.

Do you mean that it is likely to create some new issues?

However, it also looks like a change that increases the messiness of the code - moving a draws-to-screen call into a sets-invalidation-flags function. So overall I'm slightly against merging this

I could split the halo_manager::unrender method into two functions: the former would just invalidate the haloes, the latter would effectively unrender them. Then, i could call the invalidation here and the redraw here.

[stevecotton]

Do you mean that it is likely to create some new issues?

I'm worried that it will, yes.

However, I'm unfamiliar with the code and not wanting to learn a new code section, I don't know what should be done with it.

[Pentarctagon]

@mesilliac would this be made irrelevant by the rendering overhaul going on?

[mesilliac]

Hmm. Eventually yes but not yet. From a quick look this could probably just be merged, as it's a small change. I'll take a look at it later.

[mesilliac]

Verified that it works and the change is okay. Merged