we only ever need the first entry, so there's no point storing all of them. In addition, the field is private, which guarantees that nothing else needs the array either.
This also fixes phpstan/phpstan@c50650c5dd.
these types of chains would never normally occur, but they've been seen in the wild. Attempting to resolve such chains has exponentially increasing complexity.
every time a chunk passed through Level->generateChunkCallback(), it fired onChunkChanged() for chunk listeners, which in turn caused players to rerun chunk orders even though the target chunk had not been sent yet anyway.
this caused some performance issues and silent bugs with the generator, notably that the generator would always think all chunks had been changed, causing them to be re-set back into the world 9 times.
previously a file with a 4-letter name ending in 'mca' in the region folder of a PMAnvil world would cause the world format to be unrecognized. This happens because strrpos() returns false when the substring isn't found, which gets coerced to 0 when used in addition.
this has a couple of side effects which need to be explored.
- first of all, this bug prevented generateLevel() from filling in the preset from server.properties. With this fix, worlds which don't have any extra generator settings will start to be generated using server.properties settings, which is almost certainly not expected behaviour.
- preset can now be specified separately from generator in pocketmine.yml, which is nicer for users.
