Ok Button is Empty

I created a DialogWrapper for a plugin I'm working on, but for some reason the "Ok" Buton is blank. Any reason why?

package io.github.seggan.slimefunaddonplugin;

import com.intellij.openapi.actionSystem.AnActionEvent;
import com.intellij.openapi.actionSystem.CommonDataKeys;
import com.intellij.openapi.command.WriteCommandAction;
import com.intellij.openapi.ui.DialogWrapper;
import com.intellij.psi.JavaPsiFacade;
import com.intellij.psi.PsiClass;
import com.intellij.psi.PsiClassType;
import com.intellij.psi.PsiElement;
import com.intellij.psi.PsiElementFactory;
import com.intellij.psi.PsiElementVisitor;
import com.intellij.psi.PsiField;
import com.intellij.psi.PsiFile;
import com.intellij.psi.PsiJavaFile;
import com.intellij.psi.PsiMethod;
import com.intellij.psi.PsiModifier;
import com.intellij.psi.PsiModifierList;
import com.intellij.psi.util.PsiTreeUtil;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;

public class NewItemDialog extends DialogWrapper {

    private final JTextField idField = new JTextField();
    private final JTextField materialField = new JTextField();
    private final JTextField nameField = new JTextField();
    private final JTextArea loreField = new JTextArea();
    private final AnActionEvent e;

    public NewItemDialog(AnActionEvent e) {
        super(true);

        this.setTitle("Create a Slimefun Item");
        this.init();

        this.e = e;
    }

    @Nullable
    @Override
    protected JComponent createCenterPanel() {
        JPanel dialogPanel = new JPanel();

        JLabel label = new JLabel("Id");
        dialogPanel.add(label);
        dialogPanel.add(idField);

        label = new JLabel("Material");
        dialogPanel.add(label);
        dialogPanel.add(materialField);

        label = new JLabel("Name");
        dialogPanel.add(label);
        dialogPanel.add(nameField);

        label = new JLabel("Lore");
        dialogPanel.add(label);
        loreField.setPreferredSize(new Dimension(100, 100));
        dialogPanel.add(loreField);

        return dialogPanel;
    }

    @Override
    protected void doOKAction() {
        WriteCommandAction.runWriteCommandAction(e.getProject(), () -> {
            PsiFile file = e.getDataContext().getData(CommonDataKeys.PSI_FILE);
            assert file instanceof PsiJavaFile;
            PsiJavaFile javaFile = (PsiJavaFile) file;

            PsiClass mainClass = javaFile.getClasses()[0];
            if (mainClass == null) {
                System.out.println("NO CLASS");
                return;
            }

            PsiElementFactory factory = JavaPsiFacade.getInstance(e.getProject()).getElementFactory();

            PsiClassType sfisClass = factory.createTypeByFQClassName("me.mrCookieSlime.Slimefun.api.SlimefunItemStack");

            String id = idField.getText();

            PsiField field = factory.createField(id, sfisClass);
            PsiModifierList modifierList = field.getModifierList();
            modifierList.setModifierProperty(PsiModifier.PUBLIC, true);
            modifierList.setModifierProperty(PsiModifier.STATIC, true);
            modifierList.setModifierProperty(PsiModifier.FINAL, true);

            field.setInitializer(factory.createExpressionFromText(
                "new SlimefunItemStack(\n" + id + ")", sfisClass.getPsiContext()));

            PsiMethod[] ctors = mainClass.getConstructors();
            if (ctors.length == 0) {
                mainClass.add(field);
            } else {
                mainClass.addAfter(field, mainClass.getConstructors()[0]);
            }

            close(OK_EXIT_CODE);
        });
    }
}