Fixed removal of nlNL targets to break mappings

When any of the nlNL targets were disabled, ie. set to ' ', some
standard operators like 'a' could break as a result. Instead of creating
a mapping like 'aL', only the operator mapping containing only 'a' would be created,
overwriting the default. This fix only applies nlNL mappings if they
were not disabled by the user.
Fixes #92