Patch by Steve the Fiddle to trap another invalid return from Nyquist and prevent crashing Audacity

src/effects/nyquist/Nyquist.cpp

@@ -920,6 +920,13 @@ bool EffectNyquist::ProcessOne()
       return false;
    }
 
+   if (outChannels == 0) {
+      wxMessageBox(_("Nyquist returned an empty array.\n"),
+                   wxT("Nyquist"),
+                   wxOK | wxCENTRE, mParent);
+      return false;
+   }
+
    double rate = mCurTrack[0]->GetRate();
    for (i = 0; i < outChannels; i++) {
       sampleFormat format = mCurTrack[i]->GetSampleFormat();