Digitizing: don't del previous draw when loading file
Digitizing: don't del previous draw when loading file

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