common: Free payload memory also if extension header is in use

Seems like these two buffers are always different, so it should be safe
to delete both.

src/frame.cc

@@ -52,7 +52,7 @@ rtp_error_t uvgrtp::frame::dealloc_frame(uvgrtp::frame::rtp_frame *frame)
         delete frame->ext;
     }
 
-    else if (frame->payload)
+    if (frame->payload)
         delete[] frame->payload;
 
     //UVG_LOG_DEBUG("Deallocating frame, type %u", frame->type);