[R&R]getSolrUrl()

Should some checking be done for null and empty?  These values seem to pass thru and return the bad URL.

  serviceResponse = service.getSolrUrl("");
       **http://localhost:64920/v1/solr_clusters//solr      //  serviceResponse value**

  serviceResponse = service.getSolrUrl(null);
       **http://localhost:64920/v1/solr_clusters/null/solr      //  serviceResponse value**
