Fixed EditorViewport crash on keypresses

Before, EditorViewport would start accessing arrays on keypresses (specifically
the arrow keys) even when there were no editors.  This adds an extra check to
prevent this.

Source/UI/EditorViewport.cpp

@@ -522,7 +522,7 @@ bool EditorViewport::keyPressed (const KeyPress &key) {
 
    //std::cout << "Editor viewport received " << key.getKeyCode() << std::endl;
 
-   if (canEdit) 
+  if (canEdit && editorArray.size() > 0) 
    {
 
         ModifierKeys mk = key.getModifiers();