Don't use PacketBuffer#readString since it's client-only. (#4489)

Fixes #4488

src/main/java/appeng/core/sync/BasePacket.java

@@ -32,6 +32,15 @@ import appeng.core.sync.network.INetworkInfo;
 import appeng.core.sync.network.NetworkHandler;
 
 public abstract class BasePacket {
+
+    /**
+     * Sadly {@link PacketBuffer#readString()} gets inlined by Proguard which means
+     * it's not available on the Server. This field has the default string length
+     * that is used for writeString, which then also should be used for readString
+     * when it has no special length requirements.
+     */
+    public static final int MAX_STRING_LENGTH = 32767;
+
     private PacketBuffer p;
 
     public void serverPacketData(final INetworkInfo manager, final PlayerEntity player) {

src/main/java/appeng/core/sync/packets/ConfigValuePacket.java

@@ -57,8 +57,8 @@ public class ConfigValuePacket extends BasePacket {
     private final String Value;
 
     public ConfigValuePacket(final PacketBuffer stream) {
-        this.Name = stream.readString();
-        this.Value = stream.readString();
+        this.Name = stream.readString(MAX_STRING_LENGTH);
+        this.Value = stream.readString(MAX_STRING_LENGTH);
     }
 
     // api