Fix dynamic context callbacks sometimes returning null

I have noticed that in some cases result of user supplied function for custom context or custom context itself can be set to null instead of proper object. Since presence of one custom custom context not generally critical to event data - the data should not go into bad stream because logic sees null instead of context.

The solution is to sanitize user supplied contexts for “falsy” values.

In order to do that the following adjustments would be needed in helpers.js under src/js/lib sub-folder add following:

• filter = require("lodash/filter"), line right after map = require("lodash/map"), line
• Update object.resolveDynamicContexts function’s return statement and wrap returning map function in filter() i.e to this:

return filter(map(dynamicOrStaticContexts, function(context) {
			if (typeof context === 'function') {
				try {
					return context.apply(null, params);
				} catch (e) {
					//TODO: provide warning
				}
			} else {
				return context;
			}
		}));

[max-tgam]

@colmsnowplow This is what I mentioned yesterday during the call.

[max-tgam]

@szareiangm FYI