Fix export when cairosvg module is not found

If not found, the program should not try to export the image using it
anyway.

lokrez/export.py

@@ -114,6 +114,7 @@ def generate_outfile(
                             )
             log.debug(e)
 
+        else:
             svg_str = jj2_tpl.render(context)
 
             if outfilename.suffix == ".png":