fix an issue where you could move the overlay off the top of the window, and never get it back
fix an issue where you could move the overlay off the top of the window, and never get it back

Ensembl/ensembl-webcode,Ensembl/ensembl-webcode,Ensembl/ensembl-webcode,Ensembl/ensembl-webcode,Ensembl/ensembl-webcode