utils_misc.js: fix bug in escapeHtmlSpecialChars
utils_misc.js: fix bug in escapeHtmlSpecialChars

The bug does not appear in most cases, considering `div` as `'undefined'`
(resulting in valid <undefined></undefined> element)

Seems that some browsers behave differently, causing exception
fix #211

3ch01c/ingress-intel-total-conversion,Hubertzhang/ingress-intel-total-conversion,McBen/ingress-intel-total-conversion,McBen/ingress-intel-total-conversion,sndirsch/ingress-intel-total-conversion,Hubertzhang/ingress-intel-total-conversion,3ch01c/ingress-intel-total-conversion,3ch01c/ingress-intel-total-conversion,Hubertzhang/ingress-intel-total-conversion,Hubertzhang/ingress-intel-total-conversion,McBen/ingress-intel-total-conversion,Hubertzhang/ingress-intel-total-conversion,McBen/ingress-intel-total-conversion,sndirsch/ingress-intel-total-conversion,McBen/ingress-intel-total-conversion,3ch01c/ingress-intel-total-conversion,sndirsch/ingress-intel-total-conversion,3ch01c/ingress-intel-total-conversion,sndirsch/ingress-intel-total-conversion,3ch01c/ingress-intel-total-conversion,Hubertzhang/ingress-intel-total-conversion,Hubertzhang/ingress-intel-total-conversion,sndirsch/ingress-intel-total-conversion,Hubertzhang/ingress-intel-total-conversion