PR SmingHub#2123 broke the nultipart file and post sending resulting …

…in wrong multipart boudary headers and endless loop.

This commit removes the introduced problems.

Sming/Core/Data/Stream/MultipartStream.cpp

@@ -15,6 +15,10 @@
 
 IDataSourceStream* MultipartStream::getNextStream()
 {
+	if(finished) {
+		return nullptr;
+	}
+
 	// Return content, if available
 	if(bodyPart.stream != nullptr) {
 		auto stream = bodyPart.stream;
@@ -24,15 +28,18 @@ IDataSourceStream* MultipartStream::getNextStream()
 
 	// Fetch next part to send
 	bodyPart = producer();
+	if(bodyPart.headers == nullptr && bodyPart.stream == nullptr) {
+		// Nothing else to send...
+		finished = true;
+	}
 
 	// Generate header fragment
 	auto stream = new MemoryDataStream();
 	stream->ensureCapacity(4 + 16 + 4);
 	stream->print("\r\n");
 	stream->print("--");
 	stream->print(getBoundary());
-	if(bodyPart.headers == nullptr) {
-		// No more parts
+	if(finished) {
 		stream->print("--");
 	}
 	stream->print("\r\n");

Sming/Core/Data/Stream/MultipartStream.h

@@ -60,6 +60,7 @@ class MultipartStream : public MultiStream
 	Producer producer;
 	BodyPart bodyPart;
 	char boundary[16] = {0};
+	bool finished = false;
 };
 
 /**