Fixes atoms with no flags set being walkable

* Fixes atoms that have no flags set allowing movement into them regardless of CanPass(), most notably hydrotrays.

Instead of checking only atoms that do not have the ON_BORDER flag set, the if statement was instead checking for all atoms that have any flag that isn't ON_BORDER set. 

As a result, if an obstacle does not have any flags set, then it's ```CanPass()``` will never be called and the proc will exit at the ```return 1``` below.

As a side note this also caused any atoms with ON_BORDER to have their ```CanPass()``` proc called twice in a row. It seems like this bug goes all the way back to [2010](https://github.com/Baystation12/Baystation12/blame/54cdfe54bcc39f9552670b7c397752fff1b47e55/code/game/turfs/turf.dm#L89)