Pattern along path extension works only with objects converted to path

As for Bug #186582, the extention works only with objects converted to path. It is a usability issue.

The proposed solutions are similar to what I posted previously in Bug #186582:

- make the pattern along path extention automatically convert selected objects (in case there are any) to path before applying the effect AND tell about the undergoing conversion to the user (a dialog box saying "The selected objects will be converted to path" and OK / CANCEL buttons)

OR

- if among the selected objects is at least one that is not converted to paths (like a circle or a rectangle) then a dialog window could pop-up to thell the user to convert objects to path. Something like "Please convert selected objects to paths before applying this effect" and an OK button that just closes the dialog and returns the user to the canvas. No error is displayed which is a lot more user friendly that the current behaviour.