Fix crash when intercepting URLSessionUploadTask. (#133)

Per https://developer.apple.com/documentation/foundation/urlsession/1411518-uploadtask, body data parameter may be null.

Author: VaslD

Sources/NetworkInjector+URLSession.swift

@@ -316,19 +316,18 @@ extension NetworkInjector {
 
         // For safety, we should cast to AnyObject
         // To prevent app crashes in the future if the object type is changed
-        typealias NewClosureType =  @convention(c) (AnyObject, Selector, AnyObject, AnyObject, AnyObject) -> AnyObject
+        typealias NewClosureType =  @convention(c) (AnyObject, Selector, AnyObject, AnyObject?, AnyObject) -> AnyObject
         let originalImp: IMP = method_getImplementation(method)
-        let block: @convention(block) (AnyObject, AnyObject, AnyObject, AnyObject) -> AnyObject = {[weak self](me, request, data, block) in
+        let block: @convention(block) (AnyObject, AnyObject, AnyObject?, AnyObject) -> AnyObject = {[weak self](me, request, data, block) in
 
             // call the original
             let original: NewClosureType = unsafeBitCast(originalImp, to: NewClosureType.self)
             let task = original(me, selector, request, data, block)
 
             // Safe-check
             if let task = task as? URLSessionTask,
-               let request = request as? NSURLRequest,
-               let data = data as? Data {
-                self?.delegate?.injectorSessionDidUpload(task: task, request: request, data: data)
+               let request = request as? NSURLRequest {
+                self?.delegate?.injectorSessionDidUpload(task: task, request: request, data: data as? Data)
             } else {
                 assertionFailure("Could not get data from _swizzleURLSessionUploadSelector. It might causes due to the latest iOS changes. Please contact the author!")
             }