Fix crash in legacy service (#2437)

Bug in #2360

lib/request-handler.js

@@ -74,6 +74,10 @@ function flattenQueryParams(queryParams) {
 //
 // Pass just the handler function as shorthand.
 function handleRequest(cacheHeaderConfig, handlerOptions) {
+  if (!cacheHeaderConfig) {
+    throw Error('cacheHeaderConfig is required')
+  }
+
   if (typeof handlerOptions === 'function') {
     handlerOptions = { handler: handlerOptions }
   }