NaN usage ratio in depclean-results.json

[cesarsotovalero]

When a dependency has no types, a division by zero occurs, causing the usageRatio in depclean-results.json to be NaN.

Example:

{
   "id": "com.google.guava:listenablefuture:jar:9999.0-empty-to-avoid-conflict-with-guava:test",
   "coordinates": "com.google.guava:listenablefuture:9999.0-empty-to-avoid-conflict-with-guava",
   "groupId": "com.google.guava",
   "artifactId": "listenablefuture",
   "version": "9999.0-empty-to-avoid-conflict-with-guava",
   "scope": "test",
   "packaging": "jar",
   "omitted": false,
   "size": 2199,
   "type": "transitive",
   "status": "bloated",
   "parent": "com.google.guava:guava:jar:30.1-jre:test",
   "allTypes": [],
   "usedTypes": [],
   "usageRatio": NaN,
   "children": []
}