nil is not compatible with the expected argument type '[NSObject : AnyObject]'

I am using XCode 7.2 and Swift 2.2. I have a function that accepts a dictionary([NSObject : AnyObject]) as a parameter. However, I want to call this function without using that dictionary or in other words by making the parameter nil. If I do that, this is thrown:

nil is not compatible with the expected argument type '[NSObject : AnyObject]'

My code is

self.silentPostData(
  persist.getObject(
    mdmiosagent_Constants.SERVERNAMEKEY) as String, 
    serverport: persist.getObject(mdmiosagent_Constants.SERVERPORTKEY) as String,
    serverurl:  mdmiosagent_Constants.NATIVE_APP_SERVLET,
    parameters: nil ,
    urldata: jsonData
  )
)

The parameter in conflict is named parameters in the code. Thank you in advance.