Error: [ E/flutter (10956): [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: NoSuchMethodError: The method 'call' was called on null. ]

[claudneysessa]

After the flutter update, I'm having the following problem

E/flutter (10956): [ERROR:flutter/lib/ui/ui_dart_state.cc(157)] Unhandled Exception: NoSuchMethodError: The method 'call' was called on null.
E/flutter (10956): Receiver: null
E/flutter (10956): Tried calling: call()
E/flutter (10956): #0 new DropDownFormField..
package:material_dropdown_formfield/material_dropdown_formfield.dart:157
E/flutter (10956): #1 _DropdownButtonState._handleTap.
package:flutter/…/material/dropdown.dart:1219
E/flutter (10956): #2 _rootRunUnary (dart:async/zone.dart:1192:38)
E/flutter (10956): #3 _CustomZone.runUnary (dart:async/zone.dart:1085:19)
E/flutter (10956): #4 _FutureListener.handleValue (dart:async/future_impl.dart:141:18)
E/flutter (10956): #5 Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:682:45)
E/flutter (10956): #6 Future._propagateToListeners (dart:async/future_impl.dart:711:32)
E/flutter (10956): #7 Future._completeWithValue (dart:async/future_impl.dart:526:5)
E/flutter (10956): #8 Future._asyncComplete. (dart:async/future_impl.dart:556:7)
E/flutter (10956): #9 _rootRun (dart:async/zone.dart:1184:13)
E/flutter (10956): #10 _CustomZone.run (dart:async/zone.dart:1077:19)
E/flutter (10956): #11 _CustomZone.runGuarded (dart:async/zone.dart:979:7)
E/flutter (10956): #12 _CustomZone.bindCallbackGuarded. (dart:async/zone.dart:1019:23)
E/flutter (10956): #13 _microtaskLoop (dart:async/schedule_microtask.dart:43:21)
E/flutter (10956): #14 _startMicrotaskLoop (dart:async/schedule_microtask.dart:52:5)
E/flutter (10956):