TagHandler: pass SongTime to duration()

src/decoder/plugins/WavpackDecoderPlugin.cxx

@@ -283,9 +283,10 @@ wavpack_scan_file(Path path_fs,
 		return false;
 	}
 
-	tag_handler_invoke_duration(handler, handler_ctx,
-				    WavpackGetNumSamples(wpc) /
-				    WavpackGetSampleRate(wpc));
+	const auto duration =
+		SongTime::FromScale<uint64_t>(WavpackGetNumSamples(wpc),
+					      WavpackGetSampleRate(wpc));
+	tag_handler_invoke_duration(handler, handler_ctx, duration);
 
 	/* the WavPack format implies APEv2 tags, which means we can
 	   reuse the mapping from tag_ape.c */