ReSharper 8.2: TypeScript lambda function results in incorrect static analysis

I have a TypeScript function like this:

var earliest = null;
eventList.forEach(function (event) {
     if (earliest == null || event.start < earliest) { earliest = event.start; }
}, this);
this.setEarliest(earliest);

When it's in function form, this does not warn me that earliest will always be null. But rewrite it as a lambda function:

var earliest = null;
eventList.forEach((event) => {
     if (earliest == null || event.start < earliest) { earliest = event.start; }
}, this);
this.setEarliest(earliest);