fix(find): don't look for -exec etc command if completing before it

Closes scop#509

Author: scop

completions/find

@@ -10,6 +10,7 @@ _find()
     local i
     for i in ${!words[*]}; do
         if [[ ${words[i]} == -@(exec|ok)?(dir) ]]; then
+            ((cword > i)) || break
             _command_offset $((i + 1))
             return
         fi