Описание
# Create Collision Crashfix
A tiny, single-mixin hotfix for a **server-fatal crash in Create 6.0.10** on Minecraft 1.21.1 (NeoForge).
## The problem
A moving Create contraption can hard-crash the server tick loop:
```
java.lang.NullPointerException: Cannot read field "x" because "mf.axis" is null
at com.simibubi.create.foundation.collision.ContinuousOBBCollider.collideMany(ContinuousOBBCollider.java:153)
at com.simibubi.create.content.contraptions.ContraptionCollider.collideEntities(ContraptionCollider.java:166)
at com.simibubi.create.content.contraptions.ContraptionHandler.tick(ContraptionHandler.java:54)
Description: Exception in server tick loop
```
Once it happens the world usually **crash-loops** on load, because the offending contraption fires the same crash every tick.
**When it triggers:** a moving contraption's collision check hits a degenerate, zero-distance case — an entity's bounding-box center lands *exactly* on a contraption block's center on every axis. The most common real-world trigger is a **rope pulley + drill quarry** (e.g. a drill array with the pulley in the center column), but rotating bearings, tree farms with a saw, and similar setups can also hit it.
This is an upstream Create bug, present only in **6.0.10** (6.0.9 is unaffected). The official fix is Create PR #10301, milestoned for 6.0.11, which is not released yet. Downgrading to 6.0.9 is not an option for most packs because many Create addons require `create >= 6.0.10`.
### Related upstream reports
- Issue #10218 (tracking) — https://github.com/Creators-of-Create/Create/issues/10218
- Issue #10278 — `mf.axis` is null when entity AABB center coincides with contraption block center — https://github.com/Creators-of-Create/Create/issues/10278
- Issue #10344 — https://github.com/Creators-of-Create/Create/issues/10344
- Issue #10353 — https://github.com/Creators-of-Create/Create/issues/10353
- Issue #10378 — contraption collision NPE edge cases — https://github.com/Creators-of-Create/Create/issues/10378
- Issue #10479 — tree farm crashes server when loaded — https://github.com/Creators-of-Create/Create/issues/10479
- Upstream fix: PR #10301 — https://github.com/Creators-of-Create/Create/pull/10301
## The fix — what changed and why it works
Inside Create's `ContinuousSeparationManifold#separate`, the separation `axis` (and `normalAxis`) are recorded **only when the tested distance is non-zero**:
```java
if (distance != 0.0 && -diff