[BUGFIX] Third part WMS block Map Loading
[BUGFIX] Third part WMS block Map Loading

Fixes #577

makinacorpus/lizmap-web-client,nboisteault/lizmap-web-client,3liz/lizmap-web-client,nboisteault/lizmap-web-client,jancelin/lizmap-web-client,laurentj/lizmap-web-client,makinacorpus/lizmap-web-client,rldhont/lizmap-web-client,makinacorpus/lizmap-web-client,laurentj/lizmap-web-client,jancelin/lizmap-web-client,rldhont/lizmap-web-client,3liz/lizmap-web-client,jancelin/lizmap-web-client,3liz/lizmap-web-client,3liz/lizmap-web-client,rldhont/lizmap-web-client,makinacorpus/lizmap-web-client,laurentj/lizmap-web-client,jancelin/lizmap-web-client,nboisteault/lizmap-web-client,jancelin/lizmap-web-client,makinacorpus/lizmap-web-client,jancelin/lizmap-web-client,laurentj/lizmap-web-client,nboisteault/lizmap-web-client,rldhont/lizmap-web-client