Emoji at beginning of paragraphs cause problems with Tags

[brian-superlist]

Package Version

1. super_editor main channel
2. Flutter main latest

To Reproduce
Steps to reproduce the behavior:

1. Launch the example app on macos
2. Go to the Action Tags demo
3. Try to insert the 🔴 emoji
4. See the error

Actual behavior
No emoji is inserted. Error thrown (see below)

Expected behavior
The emoji is inserted correctly.

Platform
macOS

Flutter version

[!] Flutter (Channel main, 3.20.0-17.0.pre.99, on macOS 14.2.1 23C71 darwin-arm64, locale en-US)
Dart SDK version: 3.4.0-190.0.dev (dev) (Thu Feb 29 08:14:33 2024 -0800) on "macos_arm64"

Error

======== Exception caught by services library ======================================================
The following _TypeError was thrown during method call TextInputClient.updateEditingStateWithDeltas:
Null check operator used on a null value

When the exception was thrown, this was the stack: 
#0      TagFinder.findTagAroundPosition (package:super_editor/src/default_editor/text_tokenizing/tags.dart:40:95)
#1      ActionTagComposingReaction.react (package:super_editor/src/default_editor/text_tokenizing/action_tags.dart:299:37)
#2      Editor._reactToChanges (package:super_editor/src/core/editor.dart:218:16)
#3      Editor.execute (package:super_editor/src/core/editor.dart:161:9)
#4      TextDeltasDocumentEditor._insertPlainText (package:super_editor/src/default_editor/document_ime/document_delta_editing.dart:342:12)
#5      TextDeltasDocumentEditor.insert (package:super_editor/src/default_editor/document_ime/document_delta_editing.dart:294:23)
#6      TextDeltasDocumentEditor._applyInsertion (package:super_editor/src/default_editor/document_ime/document_delta_editing.dart:171:5)
#7      TextDeltasDocumentEditor.applyDeltas (package:super_editor/src/default_editor/document_ime/document_delta_editing.dart:80:9)
#8      DocumentImeInputClient.updateEditingValueWithDeltas (package:super_editor/src/default_editor/document_ime/document_ime_communication.dart:219:30)
#9      DeltaTextInputClientDecorator.updateEditingValueWithDeltas (package:super_editor/src/default_editor/document_ime/ime_decoration.dart:129:14)
#10     TextInput._handleTextInputInvocation (package:flutter/src/services/text_input.dart:1892:63)
#11     TextInput._loudlyHandleTextInputInvocation (package:flutter/src/services/text_input.dart:1781:20)
#12     MethodChannel._handleAsMethodCall (package:flutter/src/services/platform_channel.dart:571:55)
#13     MethodChannel.setMethodCallHandler.<anonymous closure> (package:flutter/src/services/platform_channel.dart:564:34)
#14     _DefaultBinaryMessenger.setMessageHandler.<anonymous closure> (package:flutter/src/services/binding.dart:581:35)
#15     _invoke2 (dart:ui/hooks.dart:344:13)
#16     _ChannelCallbackRecord.invoke (dart:ui/channel_buffers.dart:45:5)
#17     _Channel.push (dart:ui/channel_buffers.dart:135:31)
#18     ChannelBuffers.push (dart:ui/channel_buffers.dart:343:17)
#19     PlatformDispatcher._dispatchPlatformMessage (dart:ui/platform_dispatcher.dart:750:22)
#20     _dispatchPlatformMessage (dart:ui/hooks.dart:257:31)
call: MethodCall(TextInputClient.updateEditingStateWithDeltas, [28, {deltas: [{selectionBase: 4, oldText: . , selectionAffinity: TextAffinity.downstream, deltaEnd: 2, deltaText: 🔴, deltaStart: 2, composingExtent: -1, selectionIsDirectional: false, selectionExtent: 4, composingBase: -1}]}])
====================================================================================================

Additional context
Using tags, we are also seeing this in Superlist when you:

1. Insert an emoji at the beginning of a paragraph
2. Press left arrow key (to move the arrow before the emoji)
3. The same findTagAroundPosition throws an error