Working code

neoforge/src/main/java/com/lukasabbe/bookshelfinspector/NetworkHandler.java

@@ -7,6 +7,7 @@ import com.lukasabbe.bookshelfinspector.network.packets.ModCheckPayload;
 import net.minecraft.client.player.LocalPlayer;
 import net.minecraft.server.level.ServerPlayer;
 import net.neoforged.bus.api.SubscribeEvent;
+import net.neoforged.neoforge.network.event.RegisterConfigurationTasksEvent;
 import net.neoforged.neoforge.network.event.RegisterPayloadHandlersEvent;
 import net.neoforged.neoforge.network.registration.PayloadRegistrar;
 
@@ -14,7 +15,7 @@ public class NetworkHandler {
 
     @SubscribeEvent
     public static void registerPayloads(final RegisterPayloadHandlersEvent event){
-        final PayloadRegistrar registrar = event.registrar("1");
+        final PayloadRegistrar registrar = event.registrar("bookshelfinspector").optional();
         registrar.playToClient(
                 BookShelfInventoryPayload.ID,
                 BookShelfInventoryPayload.CODEC,

neoforge/src/main/java/com/lukasabbe/bookshelfinspector/platform/NeoForgeNetworkHelper.java

@@ -8,7 +8,9 @@ import net.neoforged.neoforge.network.PacketDistributor;
 public class NeoForgeNetworkHelper implements INetworkHelper {
     @Override
     public void sendPacketFromServer(ServerPlayer player, CustomPacketPayload payload) {
-        PacketDistributor.sendToPlayer(player, payload);
+        try{
+            PacketDistributor.sendToPlayer(player, payload);
+        }catch (Exception ignored) {}
     }
 
     @Override

neoforge/src/main/resources/META-INF/neoforge.mods.toml

@@ -1,35 +1,13 @@
 modLoader = "javafml" #mandatory
 loaderVersion = "*" #mandatory
 license = "${license}" # Review your options at https://choosealicense.com/.
-#issueTrackerURL="https://change.me.to.your.issue.tracker.example.invalid/" #optional
 [[mods]] #mandatory
 modId = "${mod_id}" #mandatory
 version = "${version}" #mandatory
 displayName = "${mod_name}" #mandatory
-#updateJSONURL="https://change.me.example.invalid/updates.json" #optional (see https://docs.neoforged.net/docs/misc/updatechecker/)
-#displayURL="https://change.me.to.your.mods.homepage.example.invalid/" #optional (displayed in the mod UI)
 logoFile="${mod_id}.png" #optional
 credits="${credits}" #optional
 authors = "${mod_author}" #optional
 description = '''${description}''' #mandatory (Supports multiline text)
-displayTest = "NONE"
 [[mixins]]
-config = "${mod_id}.mixins.json"
-[[dependencies.${mod_id}]] #optional
-modId = "neoforge" #mandatory
-type="required" #mandatory (Can be one of "required", "optional", "incompatible" or "discouraged")
-versionRange = "[${neoforge_version},)" #mandatory
-ordering = "NONE" # The order that this dependency should load in relation to your mod, required to be either 'BEFORE' or 'AFTER' if the dependency is not mandatory
-side = "BOTH" # Side this dependency is applied on - 'BOTH', 'CLIENT' or 'SERVER'
-[[dependencies.${mod_id}]]
-modId = "minecraft"
-type="required" #mandatory (Can be one of "required", "optional", "incompatible" or "discouraged")
-versionRange = "${minecraft_version_range}"
-ordering = "NONE"
-side = "BOTH"
-
-# Features are specific properties of the game environment, that you may want to declare you require. This example declares
-# that your mod requires GL version 3.2 or higher. Other features will be added. They are side aware so declaring this won't
-# stop your mod loading on the server for example.
-#[features.${mod_id}]
-#openGLVersion="[3.2,)"
+config = "${mod_id}.mixins.json"