java - Worklight project upgrade error -

i encountered problem worklight project new technology me.

error while upgrading worklight project version 6.1.0.00-20131126-0630 6.1.0.01-20140821-0406 (also tried 6.1.0.02-21041216-0421). error message:

unexpected error during upgrade: java.lang.nullpointerexception @ com.worklight.upgrader.internal.zipper.addfoldertozip(zipper.java:190)  @ com.worklight.upgrader.internal.zipper.addfoldertozip(zipper.java:202) @ com.worklight.upgrader.internal.zipper.addfoldertozip(zipper.java:202)  @ com.worklight.upgrader.internal.zipper.addfolder(zipper.java:106) @ com.worklight.upgrader.internal.zipper.addfolder(zipper.java:91)  @ com.worklight.upgrader.wlupgradeengine.backupcurrentproject(wlupgradeengine.java:645) @ com.worklight.upgrader.wlupgradeengine.performupgrade(wlupgradeengine.java:294)  @ com.worklight.upgrader.wlupgradeengine.upgradeproject(wlupgradeengine.java:188) @ com.worklight.studio.plugin.upgrader.wlupgraderworkspacejob.runinworkspace(wlupgraderworkspacejob.java:127)  @ org.eclipse.core.internal.resources.internalworkspacejob.run(internalworkspacejob.java:38) @ org.eclipse.core.internal.jobs.worker.run(worker.java:53) 

eclipse java ee ide web developers.

version: kepler service release 2 build id: 20140224-0627

win8.1 x64

any or suggestions appreciated.

all builds have tried very, old.
ibm customer should download latest available ifix studio installation ibm fix central. latest should july 2015.

please try again version.

you can attempt delete wlbuildresources folder per instructions in question: worklight - fwlst1040e: android build failed: java.io.filenotfoundexception

finally, if still happening latest available ifix (see above), provide project issue reproducible debugged.