Fix resolving refrence

Author: Yavor16

multiapps-controller-core/src/main/java/org/cloudfoundry/multiapps/controller/core/helpers/v3/ConfigurationReferencesResolver.java

@@ -71,11 +71,10 @@ protected List<RequiredDependency> expandRequiredDependencyIfNecessary(Propertie
         }
 
         if (!permitsMultipleResources(dependency)) {
-            if (dependencyOwner instanceof Resource resource && resource.isOptional()) {
-                return Collections.singletonList(dependency);
-            } else {
+            if (isResourceNotOptional(dependencyOwner)) {
                 makeSureIsResolvedToSingleResource(dependency.getName(), resolvedReference.getResolvedResources());
             }
+            return Collections.singletonList(dependency);
         }
 
         if (resolvedReference.getResolvedResources()
@@ -110,6 +109,10 @@ protected List<RequiredDependency> getUpdatedRequiredDependencies(Resource resou
                        .collect(Collectors.toList());
     }
 
+    private boolean isResourceNotOptional(PropertiesContainer dependencyOwner) {
+        return !(dependencyOwner instanceof Resource resource) || !resource.isOptional();
+    }
+
     @Override
     protected RequiredDependency createRequiredDependency(Resource resource, RequiredDependency dependency) {
         return RequiredDependency.createV3()