If for some reason the Solr Output Connector loses the Solr core it is associated with (either because the core was deleted or the connection to the core was not available), there is no way to currently delete jobs associated with that Connector.
The only kludge way to get around this, is to manually clear out the INGESTSTATUS for entries corresponding to the Output Connection Name.
Ideally it would be nice to have a mechanism to force delete the jobs even if the Solr Output Connector is unable to reach its Solr Core.
While the intent of the current behavior is to probably make sure that all content associated with the core is removed on deletion of the job. There is always a use case where the Solr Core itself might contain items only from the job and if there is no Solr Core, there is no reason to attempt to delete content from the index.