[flutter_tool] Add missing toString() (#37331)

packages/flutter_tools/lib/src/commands/daemon.dart

diff --git a/packages/flutter_tools/lib/src/commands/daemon.dart b/packages/flutter_tools/lib/src/commands/daemon.dart
index e1bf5ec..9187bb5 100644
--- a/packages/flutter_tools/lib/src/commands/daemon.dart
+++ b/packages/flutter_tools/lib/src/commands/daemon.dart
@@ -663,7 +663,7 @@
           final Map<String, Object> response = await _deviceToMap(device);
           sendEvent(eventName, response);
         } catch (err) {
-          printError(err);
+          printError('$err');
         }
       });
     };