[ DDS ] Fix IsolateManager.initialize() not correctly handling Sentinel responses

Fixes https://github.com/flutter/flutter/issues/111482

Change-Id: I11eff2c140ea621550f33e2ddf0ab8092e9248db
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/259400
Commit-Queue: Ben Konyi <bkonyi@google.com>
Reviewed-by: Derek Xu <derekx@google.com>

pkg/dds/CHANGELOG.md

@@ -2,6 +2,7 @@
 - [DAP] Removed an unused parameter `resumeIfStarting` from `DartDebugAdapter.connectDebugger`.
 - [DAP] Fixed some issues where removing breakpoints could fail if an isolate exited during an update or multiple client breakpoints mapped to the same VM breakpoint.
 - [DAP] Paths provided to DAP now always have Windows drive letters normalized to uppercase to avoid some issues where paths may be treated case sensitively.
+- Fixed issue where DDS wasn't correctly handling `Sentinel` responses in `IsolateManager.initialize()`.
 
 # 2.2.6
 - Fixed an issue where debug adapters would not automatically close after terminating/disconnecting from the debugee.

pkg/dds/lib/src/isolate_manager.dart

@@ -226,6 +226,11 @@ class IsolateManager {
           final isolate = await dds.vmServiceClient.sendRequest('getIsolate', {
             'isolateId': id,
           });
+          // If the isolate has shutdown after the getVM request, ignore it and
+          // continue to the next isolate.
+          if (isolate['kind'] == 'Sentinel') {
+            continue;
+          }
           final name = isolate['name'];
           if (isolate.containsKey('pauseEvent')) {
             isolates[id] = _RunningIsolate(this, id, name);