Installing an not existing plugin uninstalls all others

[Locour]

Issue

Impacted version: 4.20
Deployment mode: native (war executed with java)

Problem description:

Installing the pages plugin without having the source jar in your pluginsfolder causes an error which additionally removes all other plugins(sources). Due to that that all sources are removed to you also cant reinstall them without fetching the sources again.
Happened during upgrade from gitbucket version 4.18 to 4.20. Used existing installation for testing.

Error message:

Internal Server Error
java.io.IOException: Unable to delete file:
...\Gitbucket\source\plugins.installed\gitbucket-pages-plugin_2.12-1.5.0.jar

org.apache.commons.io.FileUtils.forceDelete(FileUtils.java:2381)
org.apache.commons.io.FileUtils.cleanDirectory(FileUtils.java:1679)
org.apache.commons.io.FileUtils.deleteDirectory(FileUtils.java:1575)
gitbucket.core.plugin.PluginRegistry$.initialize(PluginRegistry.scala:260)
gitbucket.core.plugin.PluginRegistry$.install(PluginRegistry.scala:239)
gitbucket.core.controller.SystemSettingsControllerBase.$anonfun$$init$$20(SystemSettingsController.scala:252)
scala.Option.foreach(Option.scala:257)
gitbucket.core.controller.SystemSettingsControllerBase.$anonfun$$init$$19(SystemSettingsController.scala:246)

[takezoe]

Is something related with source jar? or what's your OS that GitBucket is worked?