Editor scripting: Object reference not set to an instance of an object

Hi!

I have a Unity Editor script, and I need to manage arrays.

I'm already correctly using two arrays, and I need a third one of int type, but even when doing the exact same process I used to get and set the data from the other two, I get the "Object reference not set to an instance of an object" error.

Where the problem could be?

First part of editor script (I get the error in GetFrameNumbersArray(), inside the "for"):

     [CustomEditor(typeof(MenuButtonsGeneratorVR))]
     public class MenuEditorVR : Editor {
 
         private SerializedObject m_Object;
 
         private SerializedProperty m_MenuItems;
         private SerializedProperty m_Textures;
         private SerializedProperty m_ScenesIndexes;
         private SerializedProperty m_Animations;
         private SerializedProperty m_FramesNumber;
 
         public void OnEnable() {
             m_Object = new SerializedObject(target);
 
             m_MenuItems = m_Object.FindProperty("m_MenuItems");
             m_Textures = m_Object.FindProperty("m_Textures");
             m_ScenesIndexes = m_Object.FindProperty("m_ScenesIndexes");
             m_Animations = m_Object.FindProperty("m_Animations");
             m_FramesNumber = m_Object.FindProperty("m_FramesNumber");
         }

         private static string framesNumberArraySizePath = "m_FramesNumber.Array.size";
         private static string framesNumberArrayData = "m_FramesNumber.Array.data[{0}]";
 
         // Get the array elements
         private int[] GetFrameNumbersArray() {
 
             var framesArray = new int[m_MenuItems.intValue];
 
             for (int i = 0; i < m_MenuItems.intValue; i++) {
                 framesArray[i] = m_Object.FindProperty(string.Format(framesNumberArrayData, i)).intValue;
             }
 
             return framesArray;
         }
 
         // Set a new array element
         private void SetFramesNumberIndex(int i, int index) {
             m_Object.FindProperty(string.Format(framesNumberArrayData, i)).intValue = index;
         }

I obviously have a m_FramesNumber public int array variable in the script affected by this, but it still throws an error when calling the GetFrameNumbersArray() method and entering the "for" statement.

Any help is really appreaciated.

Thanks for your time and have a nice day!