addVitem gets empty string for theRow.inheritedValue and displayValue. Then appendItem gets null value and returns undefined (“return” statement with no return value!), which is assigned to span.
setLang is called with node === span === undefined.
All this happens after console warning “For 472c0c2983911106 - there is INHERITANCE_MARKER without inheritedValue CldrSurveyVettingTable.js:519:15” and similar for three other paths.
So, there are two problems:
Server sends ugly data to client: winning value is INHERITANCE_MARKER but inheritedValue is empty
Client chokes on the ugly data
Top priority is to bullet-proof the client by making addVitem return early and harmlessly if displayValue is empty:
Problematic data (in the json):