GROOVY-11578: Provide a default service for when serviceloader is not working, like currently in OSGi context

Author: Roy Teeuwen

subprojects/groovy-json/src/main/java/org/apache/groovy/json/internal/FastStringUtils.java

@@ -47,7 +47,7 @@ private static FastStringService loadService() {
                     }
                 }
             }
-            return found;
+            return found != null ? found : new DefaultFastStringService();
         }
     }