Do not add non-PersistentVolume to return value for pvAssumeCache#ListPVs

pkg/controller/volume/scheduling/scheduler_assume_cache.go

@@ -396,6 +396,7 @@ func (c *pvAssumeCache) ListPVs(storageClassName string) []*v1.PersistentVolume
 		pv, ok := obj.(*v1.PersistentVolume)
 		if !ok {
 			klog.Errorf("ListPVs: %v", &errWrongType{"v1.PersistentVolume", obj})
+			continue
 		}
 		pvs = append(pvs, pv)
 	}