How to avoid Error message on designer startup

Hi Ivy team,

each time when starting Axon Ivy Designer an error box welcomes with the following content:

"An internal error occurred during: "Verify Web App Libraries". java.lang.NullPointerException".

The Designer works after closing the error message, so this is not a real problem. What is the reason for the cryptic message? Tested with Axon Ivy designer 6.7.1 Rev 55496 on Windows and Linux.

EDIT:

Eclipse error log shows:

eclipse.buildId=unknown java.version=1.8.0_144 java.vendor=Oracle Corporation BootLoader constants: OS=win32, ARCH=x86_64, WS=win32, NL=en Command-line arguments: -os win32 -ws win32 -arch x86_64

org.eclipse.core.jobs
Error
Mon Sep 11 11:28:53 CEST 2017
An internal error occurred during: "Verify Web App Libraries".

java.lang.NullPointerException
    at org.eclipse.jst.common.jdt.internal.classpath.FlexibleProjectContainer.computeClasspathEntries(FlexibleProjectContainer.java:248)
    at org.eclipse.jst.j2ee.internal.web.classpath.WebAppLibrariesContainer.computeClasspathEntries(WebAppLibrariesContainer.java:195)
    at org.eclipse.jst.j2ee.internal.web.classpath.WebAppLibrariesContainer.isOutOfDate(WebAppLibrariesContainer.java:121)
    at org.eclipse.jst.j2ee.internal.web.classpath.WebAppLibrariesContainer.refresh(WebAppLibrariesContainer.java:138)
    at org.eclipse.jst.j2ee.internal.web.classpath.WebAppLibrariesContainer$1.run(WebAppLibrariesContainer.java:78)
    at org.eclipse.core.internal.jobs.Worker.run(Worker.java:54)

In error log I see also two errors for starting BPM engine with ConnectivityDemos and QuickstartTutorial I made edits to.

EDIT 2:

Steps to reproduce:

1. select a new workspace
2. import all axonivy demo projects
3. unpack connectivityDemos and edit some label.
4. save close and restart designer

Full error log is here [1]

Best regards,

Adam

[1] http://pasted.co/c06415ae