Investigate and fix "null is not of subtype string" crash seen in processIncomingEvents

[vishalxl]

To attach pic later

Unhandled exception:
type 'Null' is not a subtype of type 'String'
#0      Store.handleChannelEvents (package:nostr_console/tree_ds.dart:815)                                #1      Store.processIncomingEvent.<anonymous closure> (package:nostr_console/tree_ds.dart:1508)          #2      SetMixin.forEach (dart:collection/set.dart:142)                                                   #3      Store.processIncomingEvent (package:nostr_console/tree_ds.dart:1445)
#4      processAnyIncomingEvents.<anonymous closure> (package:nostr_console/console_ui.dart:27)
#5      new Future.delayed.<anonymous closure> (dart:async/future.dart:424)
#6      Timer._createTimer.<anonymous closure> (dart:async-patch/timer_patch.dart:18)
#7      _Timer._runTimers (dart:isolate-patch/timer_impl.dart:398)
#8      _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:429)
#9      _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:192)

[vishalxl]

This was fixed in a build on 4 jan 2023.

[vishalxl]

Was fixed in commit here

To be included in release 0.3.5-beta.

[vishalxl]

release with fix is 0.3.5-beta