Fix compilation

Author: DRSchlaubi

gradle.properties

@@ -1,3 +1,6 @@
 kotlin.code.style=official
 #dokka will run out of memory with the default meta space
 org.gradle.jvmargs=-XX:MaxMetaspaceSize=1024m
+# https://kotlinlang.org/docs/dokka-migration.html#set-the-opt-in-flag
+org.jetbrains.dokka.experimental.gradle.pluginMode=V2Enabled
+org.jetbrains.dokka.experimental.gradle.pluginMode.noWarn=true