Nyquist: Handle nyx_list return value

Required to avoid error on running Macoro Scripting commands
from Nyquist.

src/effects/nyquist/Nyquist.cpp

@@ -613,7 +613,7 @@ bool NyquistEffect::Process()
       mDelegate.reset();
       return result;
    }
-   
+
    // Check for reentrant Nyquist commands.
    // I'm choosing to mark skipped Nyquist commands as successful even though
    // they are skipped.  The reason is that when Nyquist calls out to a chain,
@@ -1412,6 +1412,16 @@ bool NyquistEffect::ProcessOne()
       return false;
    }
 
+   if (rval == nyx_list) {
+      wxLogMessage("Nyquist returned nyx_list");
+      if (GetType() == EffectTypeTool) {
+         mProjectChanged = true;
+      } else {
+         Effect::MessageBox(XO("Nyquist returned a list.") );
+      }
+      return true;
+   }
+
    if (rval == nyx_string) {
       // Assume the string has already been translated within the Lisp runtime
       // if necessary, by gettext or ngettext defined below, before it is