input_stream: added function input_stream_deinit()

All close() implementations must call this method.

src/input_stream.c

@@ -99,8 +99,6 @@ input_stream_read(struct input_stream *is, void *ptr, size_t size,
 
 void input_stream_close(struct input_stream *is)
 {
-	g_free(is->mime);
-
 	is->plugin->close(is);
 }