fix missing virtual destructors as reported in #1386

core/src/dsp/stream.h

@@ -11,6 +11,7 @@
 namespace dsp {
     class untyped_stream {
     public:
+        virtual ~untyped_stream() {}
         virtual bool swap(int size) { return false; }
         virtual int read() { return -1; }
         virtual void flush() {}