Correctly retrun true for empty input shapes in EntityGetter#isUnobstructed

Vanilla will return true for empty shapes, so we should as well.

src/main/java/ca/spottedleaf/moonrise/mixin/collisions/EntityGetterMixin.java

@@ -74,7 +74,7 @@ interface EntityGetterMixin {
     @Overwrite
     default boolean isUnobstructed(final Entity entity, final VoxelShape voxel) {
         if (voxel.isEmpty()) {
-            return false;
+            return true;
         }
 
         final AABB singleAABB = ((CollisionVoxelShape)voxel).moonrise$getSingleAABBRepresentation();

src/main/java/ca/spottedleaf/moonrise/mixin/collisions/LevelMixin.java

@@ -55,7 +55,7 @@ abstract class LevelMixin implements LevelAccessor, AutoCloseable {
     public boolean isUnobstructed(final Entity entity) {
         final AABB boundingBox = entity.getBoundingBox();
         if (CollisionUtil.isEmpty(boundingBox)) {
-            return false;
+            return true;
         }
 
         final List<Entity> entities = this.getEntities(