stable-1.2 branch, elementary os Loki, also happened on RC2 on windows 10.

If you have a sample track and put a VST effect on it, it won't export, you only get silence.

Steps to reproduce:

1. Put a sample in the sample track
2. Add a VST effect (Ambiance reverb in my case)
3. Export

When playing back the file everything works as expected and the master channel meter shows output, however when you export the master channel meter shows no activity at all. This does not happen if the sample track has a ladspa effect attached to it.

This bug does not exist in 1.1.3

Tagging @BaraMGB as they did a lot of changes concerning the sample tracks recently, so they might have some insight.