add type info to list

Author: denrase

dart/lib/src/protocol/contexts.dart

@@ -293,8 +293,7 @@ class Contexts extends MapView<String, dynamic> {
       Contexts(
         device: device ?? this.device,
         operatingSystem: operatingSystem ?? this.operatingSystem,
-        runtimes: runtimes ??
-            this[SentryRuntime.listType], // Don't use unmodifiable list here.
+        runtimes: runtimes ?? (this[SentryRuntime.listType] as List<SentryRuntime>?) ?? <SentryRuntime>[],
         app: app ?? this.app,
         browser: browser ?? this.browser,
         gpu: gpu ?? this.gpu,