The variable m_Font of 'GUISkin' doesn't exist anymore

Hi, i got a error here while i was trying to edit a GUI.Textfield in game, and dont know how to fix it, i know it says “You probably need to reassign the m_Font variable of the ‘GUISkin’ script in the inspector.” but what does that mean? this is the error:

MissingReferenceException: The variable m_Font of 'GUISkin' doesn't exist anymore.
You probably need to reassign the m_Font variable of the 'GUISkin' script in the inspector.
UnityEngine.GUI.DoTextField (Rect position, Int32 id, UnityEngine.GUIContent content, Boolean multiline, Int32 maxLength, UnityEngine.GUIStyle style) (at C:/BuildAgent/work/cac08d8a5e25d4cb/Runtime/ExportGenerated/Editor/GUI.cs:642)

The error means that the value of the variable m_Font has become null and has no valid value. Several situations can lead to this:

  1. The variable value was never assigned in the inspector.
  2. The variable value was cleared from the inspector
  3. The variable was declared but never assigned in code
  4. The variable was assigned a null value I’m code