fix(navigation/movecanvas): hook up with canvas focused state

Related to #662

lib/navigation/movecanvas/MoveCanvas.js

@@ -43,7 +43,7 @@ export default function MoveCanvas(eventBus, canvas) {
   // allow others to hook into the event before us though
   // (dragging / element moving will do this)
   eventBus.on('element.mousedown', 500, function(e) {
-    return handleStart(e.originalEvent);
+    return canvas.isFocused() && handleStart(e.originalEvent);
   });