Suppress stream subscription error

runtime/observatory/lib/src/elements/debugger.dart

Index: runtime/observatory/lib/src/elements/debugger.dart
diff --git a/runtime/observatory/lib/src/elements/debugger.dart b/runtime/observatory/lib/src/elements/debugger.dart
index dddacf0cf7c6c20e3fc29057c9f437541ee7482a..a608512133b9613f6dd136f7b4e31dbb25c9b97e 100644
--- a/runtime/observatory/lib/src/elements/debugger.dart
+++ b/runtime/observatory/lib/src/elements/debugger.dart
@@ -1706,8 +1706,20 @@ class DebuggerPageElement extends ObservatoryElement {
         app.vm.listenEventStream(VM.kDebugStream, debugger.onEvent);
     _stdoutSubscriptionFuture =
         app.vm.listenEventStream(VM.kStdoutStream, debugger.onStdout);
+    if (_stdoutSubscriptionFuture != null) {
+      // TODO(turnidge): How do we want to handle this in general?
+      _stdoutSubscriptionFuture.catchError((e, st) {
+        Logger.root.info('Failed to subscribe to stdout: $e\n$st\n');
+      });
+    }
     _stderrSubscriptionFuture =
         app.vm.listenEventStream(VM.kStderrStream, debugger.onStderr);
+    if (_stderrSubscriptionFuture != null) {
+      // TODO(turnidge): How do we want to handle this in general?
+      _stderrSubscriptionFuture.catchError((e, st) {
+        Logger.root.info('Failed to subscribe to stderr: $e\n$st\n');
+      });
+    }
     _logSubscriptionFuture =
         app.vm.listenEventStream(Isolate.kLoggingStream, debugger.onEvent);
     // Turn on the periodic poll timer for this page.