Note that tat method will make an outline whose thickness will half overlap the text-cropped image. If you want the border outside the text try this:
1. Create a new layer behind the cropped text.
2. Fill it with whatever color etc. you want the border to be.
3. Select the vector text and do a selection from vector object.
3. Switch to the new layer and do an expansion of the selection by however many pixels you want as the width of the border.
4. Invert the selection and hit Delete. What's left will form a border around the cropped image text.
You can use this to add a border around anything. I used it as the basis (with some hand-tweaking after the expansion) of the wall behind my
Gangsta '84 design, for example, and to add a black outline around my
Evacuation Route design I added today, as an afterthought after remembering the dark apparel won't take back images.