Force nil query to empty vector.
Force nil query to empty vector.

acthp/ucsc-xena-server,acthp/ucsc-xena-server,ucscXena/ucsc-xena-server,ucscXena/ucsc-xena-server,acthp/ucsc-xena-server,ucscXena/ucsc-xena-server,acthp/ucsc-xena-server,ucscXena/ucsc-xena-server,ucscXena/ucsc-xena-server,acthp/ucsc-xena-server