_overlay != null': is not true.

[BlastTea]

_overlayEntry is null, you can check that at dropdown_texfield.dart line 332, Here's the Stack Trace

The following assertion was thrown while dispatching notifications for FocusNode:
'package:flutter/src/widgets/overlay.dart': Failed assertion: line 207 pos 12: '_overlay != null': is not true.

When the exception was thrown, this was the stack:
#2      OverlayEntry.remove (package:flutter/src/widgets/overlay.dart:207:12)
overlay.dart:207
#3      DropdownTextFieldState.initialize.<anonymous closure> (package:flutter_dropdown_plus/dropdown_textfield.dart:332:25)
dropdown_textfield.dart:332
#4      ChangeNotifier.notifyListeners (package:flutter/src/foundation/change_notifier.dart:433:24)
change_notifier.dart:433
#5      FocusNode._notify (package:flutter/src/widgets/focus_manager.dart:1090:5)
focus_manager.dart:1090
#6      FocusManager.applyFocusChangesIfNeeded (package:flutter/src/widgets/focus_manager.dart:1850:12)
focus_manager.dart:1850
(elided 4 frames from class _AssertionError and dart:async)

The FocusNode sending notification was: FocusNode#e47ee([PRIMARY FOCUS])
    context: Focus
    PRIMARY FOCUS
════════════════════════════════════════════════════════════════════════════════```