Merge pull request #54 from Parsely/fix/guard-accumulators

Guard against using nonexistant accumulator values.

Author: aldraco

ParselyTracker/EngagedTime.swift

@@ -40,6 +40,10 @@ class EngagedTime: Sampler {
     func endInteraction() {
         os_log("Ending Interaction", log: OSLog.tracker, type: .debug)
         for (url, _) in accumulators {
+            guard var _ = accumulators[url] else {
+                os_log("No accumulator found for %s, skipping endInteraction", log: OSLog.tracker, type:.debug, url)
+                return
+            }
             accumulators[url]!.isEngaged = false
         }
     }

ParselyTracker/Sampler.swift

@@ -139,7 +139,10 @@ class Sampler {
     }
 
     private func sendHeartbeat(key: String) -> Void {
-        var trackedData = accumulators[key]!
+        guard var trackedData = accumulators[key] else {
+            os_log("No accumulator found for %s, skipping sendHeartbeat", log: OSLog.tracker, type:.debug, key)
+            return
+        }
         let incSecs: TimeInterval = trackedData.accumulatedTime
         if incSecs > 0 {
             os_log("Sending heartbeat for %s", log: OSLog.tracker, type:.debug, key)