fix empty null datum for realsies

src/main/java/at/petrak/hexcasting/api/item/DataHolder.java

@@ -30,6 +30,11 @@ public interface DataHolder {
         }
     }
 
+    @Nullable
+    default SpellDatum<?> emptyDatum(ItemStack stack) {
+        return null;
+    }
+
     boolean canWrite(ItemStack stack, @Nullable SpellDatum<?> datum);
 
     void writeDatum(ItemStack stack, @Nullable SpellDatum<?> datum);

src/main/java/at/petrak/hexcasting/common/casting/operators/OpRead.kt

@@ -12,11 +12,13 @@ object OpRead : ConstManaOperator {
     override fun execute(args: List<SpellDatum<*>>, ctx: CastingContext): List<SpellDatum<*>> {
         val (handStack, hand) = ctx.getHeldItemToOperateOn {
             val item = it.item
-            item is DataHolder && item.readDatum(it, ctx.world) != null
+            item is DataHolder && (item.readDatum(it, ctx.world) != null || item.emptyDatum(it) != null)
         }
 
         val handItem = handStack.item
-        val datum = (handItem as? DataHolder)?.readDatum(handStack, ctx.world) ?: throw MishapBadOffhandItem.of(handStack, hand, "iota.read")
+        val datum = (handItem as? DataHolder)?.readDatum(handStack, ctx.world)
+            ?: (handItem as? DataHolder)?.emptyDatum(handStack)
+            ?: throw MishapBadOffhandItem.of(handStack, hand, "iota.read")
 
         return listOf(datum)
     }

src/main/java/at/petrak/hexcasting/common/casting/operators/OpTheCoolerRead.kt

@@ -25,7 +25,9 @@ object OpTheCoolerRead : ConstManaOperator {
         ctx.assertEntityInRange(target)
 
 
-        val datum = item.readDatum(stack, ctx.world) ?: throw MishapBadItem.of(stack, "iota.read")
+        val datum = item.readDatum(stack, ctx.world)
+            ?: item.emptyDatum(stack)
+            ?: throw MishapBadItem.of(stack, "iota.read")
         return listOf(datum)
     }
 }

src/main/java/at/petrak/hexcasting/common/items/ItemFocus.java

@@ -28,16 +28,21 @@ public class ItemFocus extends Item implements DataHolder {
     @Override
     public @Nullable CompoundTag readDatumTag(ItemStack stack) {
         if (!stack.hasTag()) {
-            return SpellDatum.make(Widget.NULL).serializeToNBT();
+            return null;
         }
         var tag = stack.getTag();
         if (!tag.contains(TAG_DATA, Tag.TAG_COMPOUND)) {
-            return SpellDatum.make(Widget.NULL).serializeToNBT();
+            return null;
         }
 
         return tag.getCompound(TAG_DATA);
     }
 
+    @Override
+    public @Nullable SpellDatum<?> emptyDatum(ItemStack stack) {
+        return SpellDatum.make(Widget.NULL);
+    }
+
     @Override
     public boolean canWrite(ItemStack stack, SpellDatum<?> datum) {
         return !stack.hasTag() || !stack.getTag().getBoolean(TAG_SEALED);

src/main/java/at/petrak/hexcasting/common/items/ItemSpellbook.java

@@ -43,7 +43,6 @@ public class ItemSpellbook extends Item implements DataHolder {
         var tag = stack.getOrCreateTag();
         if (tag.contains(TAG_SELECTED_PAGE, Tag.TAG_ANY_NUMERIC)) {
             var pageIdx = tag.getInt(TAG_SELECTED_PAGE);
-            var pages = tag.getCompound(ItemSpellbook.TAG_PAGES);
             int highest = HighestPage(stack);
             if (highest != 0) {
                 tooltip.add(new TranslatableComponent("hexcasting.tooltip.spellbook.page",
@@ -98,7 +97,7 @@ public class ItemSpellbook extends Item implements DataHolder {
     @Override
     public @Nullable CompoundTag readDatumTag(ItemStack stack) {
         if (!stack.hasTag()) {
-            return SpellDatum.make(Widget.NULL).serializeToNBT();
+            return null;
         }
         var tag = stack.getTag();
 
@@ -114,13 +113,18 @@ public class ItemSpellbook extends Item implements DataHolder {
             if (pagesTag.contains(key)) {
                 return pagesTag.getCompound(key);
             } else {
-                return SpellDatum.make(Widget.NULL).serializeToNBT();
+                return null;
             }
         } else {
-            return SpellDatum.make(Widget.NULL).serializeToNBT();
+            return null;
         }
     }
 
+    @Override
+    public @Nullable SpellDatum<?> emptyDatum(ItemStack stack) {
+        return SpellDatum.make(Widget.NULL);
+    }
+
     @Override
     public boolean canWrite(ItemStack stack, SpellDatum<?> datum) {
         return true;

src/main/java/at/petrak/hexcasting/common/items/magic/ItemManaHolder.java

@@ -85,7 +85,7 @@ public abstract class ItemManaHolder extends Item implements ManaHolder {
     @Override
     public void appendHoverText(ItemStack pStack, @Nullable Level pLevel, List<Component> pTooltipComponents,
         TooltipFlag pIsAdvanced) {
-        if (pIsAdvanced.isAdvanced()) {
+        if (pIsAdvanced.isAdvanced() && getMaxMana(pStack) > 0) {
             pTooltipComponents.add(
                 new TranslatableComponent("item.hexcasting.manaholder.amount",
                     String.format("%,d", getMana(pStack)),