logging IviId instead of WindowId in case of error.

multiscreen-compositor/qml/main.qml

@@ -405,7 +405,7 @@ WaylandCompositor {
             var affectedSurfaces = getActiveSurfaces(getPidFromIviId(windowid));
             if (affectedSurfaces.length === 0)
             {
-                console.log("no screens found for ID", screenid);
+                console.log("no screens found for ID", windowid);
                 server.returnStatus(-1);
                 return;
             }