Do not use fWriter functions, when it has not been instantiated properly.

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@32122 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/kits/media/MediaWriter.cpp

@@ -61,6 +61,7 @@ MediaWriter::~MediaWriter()
 {
 	CALLED();
 
+	if (fWriter != NULL) {
 		// free all stream cookies
 		// and chunk caches
 		StreamInfo* info;
@@ -68,6 +69,7 @@ MediaWriter::~MediaWriter()
 			fWriter->FreeCookie(info->cookie);
 
 		_plugin_manager.DestroyWriter(fWriter);
+	}
 
 	// fTarget is owned by the BMediaFile
 }
@@ -99,6 +101,9 @@ MediaWriter::CreateEncoder(Encoder** _encoder,
 {
 	CALLED();
 
+	if (fWriter == NULL)
+		return B_NO_INIT;
+
 	// TODO: Here we should work out a way so that if there is a setup
 	// failure we can try the next encoder.
 	Encoder* encoder;