ls() queries are intended to find a single object, but
ls always returns a list (or, in older Mayas, a single
None). This creates complicated error checking for a simple question.
The easiest way to get a single value from an
ls under any circumstances is
result = (cmds.ls('your query here') or [None])
or guarantees that at a minimum you'll get a list containing a single
None so you can always index into it.
Note that this style won't tell you if you've got more than one result -- it just makes it safe to assume a single result.