NPE on map upload

java.lang.NullPointerException: entry
        at java.util.zip.ZipFile.getInputStream(ZipFile.java:361)
        at lcsb.mapviewer.converter.OverviewParser.parseOverviewLinks(OverviewParser.java:162)

reported by @nils.christian

created branch 437-npe-on-map-upload

mentioned in merge request !330 (merged)

closed via merge request !330 (merged)

mentioned in commit a78f1362