Update DesktopAgent.md

Clarified the passing of context when adding a listener

website/versioned_docs/version-2.1/api/ref/DesktopAgent.md

@@ -63,7 +63,7 @@ addContextListener(contextType: string | null, handler: ContextHandler): Promise
 
 Adds a listener for incoming context broadcasts from the Desktop Agent (via a User channel or [`fdc3.open`](#open) API call). If the consumer is only interested in a context of a particular type, they can specify that type. If the consumer is able to receive context of any type or will inspect types received, then they can pass `null` as the `contextType` parameter to receive all context types.
 
-Context broadcasts are primarily received from apps that are joined to the same User Channel as the listening application, hence, if the application is not currently joined to a User Channel no broadcasts will be received from channels. If this function is called after the app has already joined a channel and the channel already contains context that would be passed to the context listener, then it will be called immediately with that context.
+Context broadcasts are primarily received from apps that are joined to the same User Channel as the listening application, hence, if the application is not currently joined to a User Channel no broadcasts will be received from channels. If this function is called after the app has already joined a channel and the channel already contains context that matches the type of the context listener, then it will be called immediately and the context passed to the handler function. If `null` was passed as the context type for the listener and the channel contains context, then the handler function will be called immediately with the most recent context - regardless of type.
 
 Context may also be received via this listener if the application was launched via a call to [`fdc3.open`](#open), where context was passed as an argument. In order to receive this, applications SHOULD add their context listener as quickly as possible after launch, or an error MAY be returned to the caller and the context may not be delivered. The exact timeout used is set by the Desktop Agent implementation, but MUST be at least 15 seconds.