JavaFx IllegalStateException: Location is not set

Question

I'm trying to do a simples javafx application, but the code of my course just doesn't work on Intellij. I need help cous I'm with this problem a few days and just cannot find an answer for my problem, please help me to solve this problem.

Here's my main code:

    @Override
    public void start(Stage primaryStage) {
        try {
            FXMLLoader loader = new FXMLLoader(getClass().getResource("gui/MainView.fxml"));
            ScrollPane scrollPane = loader.load();

            scrollPane.setFitToHeight(true);
            scrollPane.setFitToWidth(true);

            Scene mainScene = new Scene(scrollPane);
            primaryStage.setScene(mainScene);
            primaryStage.setTitle("Sample JavaFX application");
            primaryStage.show();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

And the exception:

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$159(LauncherImpl.java:182)
    at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.IllegalStateException: Location is not set.
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2434)
    at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2409)
    at sample.Main.start(Main.java:17)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$166(LauncherImpl.java:863)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$179(PlatformImpl.java:326)
    at com.sun.javafx.application.PlatformImpl.lambda$null$177(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$178(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$152(WinApplication.java:177)
    ... 1 more
Exception running application sample.Main

Process finished with exit code 1

I've tried everything to solve this, but I dont get it. Thanks if anyone can help me.

@Edit: My fxml file:

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.Menu?>
<?import javafx.scene.control.MenuBar?>
<?import javafx.scene.control.MenuItem?>
<?import javafx.scene.control.ScrollPane?>
<?import javafx.scene.layout.VBox?>


<ScrollPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.172-ea" xmlns:fx="http://javafx.com/fxml/1">
   <content>
      <VBox prefHeight="299.0" prefWidth="448.0">
         <children>
            <MenuBar>
              <menus>
                <Menu mnemonicParsing="false" text="Registration">
                  <items>
                    <MenuItem mnemonicParsing="false" text="Seller" />
                        <MenuItem mnemonicParsing="false" text="Department" />
                  </items>
                </Menu>
                <Menu mnemonicParsing="false" text="Help">
                  <items>
                    <MenuItem mnemonicParsing="false" text="About" />
                  </items>
                </Menu>
              </menus>
            </MenuBar>
         </children>
      </VBox>
   </content>
</ScrollPane>