(MIDRC-153): Fix explorer table header sorting issue

[ocshawn]

Link to JIRA ticket if there is one: MIDRC-153

Bug Fixes

• Fix explorer table header sorting issue

[paulineribeyre]

number 0 should not be treated as empty, and empty numbers are not of type "number"

var test = null;
typeof test
"object"

var test = undefined;
typeof test
"undefined"

var test = 0;
typeof test
"number"