Description
When a core fails to be created for some reason (errant schema or solrconfig etc.), SolrCore.deleteUnloadedCore() is called from unload() in CoreContainer in order to clean-up the possibly left-over dataDir and instanceDir. The problem is that the CoreDescriptor passed to SolrCore.deleteUnloadedCore() will have its value for dataDir set to just "data/" unless an explicit dataDir was specified by the user in the request to create the core, leading to an attempt to delete simply "data/", which presumably resolves to a non-existent directory under Solr's home directory or some such.