fix(strings): work around nounset

Author: akinomyoga

completions/strings

@@ -38,8 +38,8 @@ _comp_cmd_strings()
         [[ ${COMPREPLY-} == *= ]] && compopt -o nospace
         return
     elif [[ $cur == @* ]]; then
-        _comp_compgen -c "${cur:1}" filedir
-        COMPREPLY=("${COMPREPLY[@]/#/@}")
+        _comp_compgen -c "${cur:1}" filedir &&
+            COMPREPLY=("${COMPREPLY[@]/#/@}")
         return
     fi