[1.19.2] Cannot invoke "net.minecraft.network.syncher.SynchedEntityData$DataItem.getValue()" because "dataitem" is null

[Novality]

Error when trying to summon entity:

[12:09:12] [Server thread/WARN] [minecraft/EntityType]: Exception loading entity: 
java.lang.NullPointerException: Cannot invoke "net.minecraft.network.syncher.SynchedEntityData$DataItem.getValue()" because "dataitem" is null

I followed these docs to create what I have below in my entity class:

public abstract class Dinosaur extends Animal {
    
    static final EntityDataAccessor<Integer> serum = SynchedEntityData.defineId(Dinosaur.class, EntityDataSerializers.INT);
    
    protected Dinosaur(EntityType<? extends Animal> e, Level l) {
        super(e, l);
    }
    
    public boolean isJuvenile() {
        return this.isBaby() && this.getSerum() > 0;
    }
    
    @Override
    public void tick() {
        super.tick();
        if (this.getSerum() >= 4) {
            this.age = 0;
            if (this.isBaby()) {
                this.setBaby(false);
            }
        }
        else {
            if (!this.isBaby()) {
                this.setBaby(true);
            }
            this.age = -20;
        }
    }
    
    @Override
    public void defineSynchedData() {
        this.entityData.define(serum, 1);
    }
    
    public void addSerum() {
        int s = this.getSerum();
        this.getEntityData().set(serum, s++);
    }
    
    public int getSerum() {
        return this.getEntityData().get(serum);
    }

}

Any help is greatly appreciated, thank you

[Novality]

Forgot to call defineSynchedData's super method. Case closed.

[Vakror]

wdym?I'm having this issue as well

[btuh]

me too, but in my case, the EntityDataAccessor is null

Edited September 8, 2023 by btuh