Fixes (#75)

* fixing a crash when passing null as options

Author: milos1290

Leanplum-Unity-SDK/Assets/LeanplumSDK/Apple/LeanplumApple.cs

@@ -410,7 +410,7 @@ public override void DefineAction(string name, Constants.ActionKind kind, Action
             }
 
             string argString = args == null ? null : args.ToJSON();
-            string optionString = options == null ? null : Json.Serialize(options);
+            string optionString = options == null ? "" : Json.Serialize(options);
 
             _defineAction(name, (int) kind, argString, optionString);
         }

Leanplum-Unity-SDK/Assets/Plugins/iOS/LeanplumIOSBridge.mm

@@ -371,6 +371,10 @@ void _defineAction(const char* name, int kind, const char *args, const char *opt
         NSDictionary *optionsDictionary = [NSJSONSerialization JSONObjectWithData:optionsData
                                                                    options:NSUTF8StringEncoding
                                                                      error:nil];
+        if (optionsDictionary == nil) {
+            optionsDictionary = @{};
+        }
+
 
         NSMutableArray *arguments = [NSMutableArray new];