Don't add icon separator if there is no icon for a status module

[j-xella]

When rendering status modules, there is a separator between the icon and the module text. Before, it was redundantly shown even when the module icon was disabled by the user.

[vdbe]

A better way to do this is before the echo check if an icons is empty and clear $show_icon if so

if [ -z "$icon] ; then
  show_icon=""
fi

[j-xella]

Reimplemented, please have a look

[j-xella]

It could possibly fix #85