Error: Invalid value for <polygon> attribute points="NaN,NaN NaN,NaN NaN,NaN NaN,NaN NaN,NaN NaN,NaN NaN,NaN"

I'm getting this error sometimes on refresh when using html5 krpano viewer version 1.18.
Managed to figure out that at this moment while view object exists its vlookat and hlookat properties are NaN. No errors in krpano console. This is chrome browser dev console output.

Error: Invalid value for <polygon> attribute points="NaN,NaN NaN,NaN NaN,NaN NaN,NaN NaN,NaN NaN,NaN NaN,NaN" VM308:1
$g @ VM308:1
Yb @ VM308:1
me @ VM308:1
wg @ VM308:1
ef @ VM308:1
(anonymous function) @ VM308:1
Qf @ VM308:1
(anonymous function) @ VM308:1
ea.loadfile2.l @ VM308:1
ea.loadfile2.n.onreadystatechange @ VM308:1

How do I debug this? Is there any way to find out where it all goes wrong? Sometimes it leads to panorama not being rendered and only black screen showing. Sometimes panorama does render. But majority of refreshes goes without problem.

Any ideas?

This was due to event onviewchange being called several times before onloadcomplete. Don't know if this is intended behaviour but checking if onloadcomplete happened before addressing elements in onviewchange handler solved the issue.