Fix dart-json parsing broken by print message

Print message related to suite, instead of a specific test, would break parsing - it would expect test object to be present in dictionary but there would be none.
This fix adds necessary check and messages not related to tracked tests will be ignored.

reports/dart/test/main_test.dart

@@ -24,4 +24,6 @@ void main() {
       throw Exception('Some error');
     });
   });
+
+  print('Hello from the test');
 }