"Illegal reflective access" warning with GanttProject 2.8.10

Gantt version:

GanttProject 2.8.10 Pilsen (build 2363)

Platform: OSX Catalina with java installed

$ sw_vers -productVersion
10.15.4

$ java -version
openjdk version "14" 2020-03-17
OpenJDK Runtime Environment (build 14+36-1461)
OpenJDK 64-Bit Server VM (build 14+36-1461, mixed mode, sharing)

Problem:

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by com.itextpdf.text.pdf.MappedRandomAccessFile$1 (file:/Applications/GanttProject.app/Contents/Java/plugins-2.8.10/org.ganttproject.impex.htmlpdf/lib/itextpdf-5.3.1.jar) to method java.nio.DirectByteBuffer.cleaner()
WARNING: Please consider reporting this to the maintainers of com.itextpdf.text.pdf.MappedRandomAccessFile$1
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

This is not a blocker but you probably want to take a look at it…