Fix NullPointerException

✅ Solution

NullPointerException errors often occur when code attempts to dereference a null object, such as calling a method on a variable that hasn't been initialized or assigned a value. Fix this by ensuring all objects are properly initialized, and use null checks (e.g., `if (object != null)`) before accessing their members to prevent dereferencing null values. Specifically check for unpopulated Maps (like `exceptionMappers`) and ensure they are correctly initialized before use.