[RESOLVIDO] Erro ao executar App JavaFX

Estou executando um programa simples em JavaFX que carrega os elementos de uma ComboBox, na primeira vez que executei ele rodou, porém os elementos da ComboBox não carregaram.

Percebi que eu tinha duas classes main, uma para o ComboBox outra default e resolvi deletar a default e deixar apenas a MainComboBox porém ao executar no NetBeans foi exibido o seguinte erro:

Executing C:\Users\eder\Documents\NetBeansProjects\JavaFXBasico\dist\run762557124\JavaFXBasico.jar using platform C:\Program Files\Java\jdk1.8.0_221\jre/bin/java

out 15, 2019 3:26:59 PM javafx.fxml.FXMLLoader$ValueElement processValue

WARNING: Loading FXML document with JavaFX API of version 11.0.1 by JavaFX runtime of version 8.0.221

Exception in Application start method

java.lang.reflect.InvocationTargetException

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

at java.lang.reflect.Method.invoke(Method.java:498)

at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)

at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

at java.lang.reflect.Method.invoke(Method.java:498)

at sun.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)

Caused by: java.lang.RuntimeException: Exception in Application start method

at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)

at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$1(LauncherImpl.java:182)

at java.lang.Thread.run(Thread.java:748)