fix media_basename variable check

workflow/process_episode.bash

@@ -430,9 +430,9 @@ function check_variable_is_correct() {
         fi
       ;;
       media_basename)
-        if [[ ! -s "${media_basename}" || -z "${media_basename}" ]]
+        if [ -z "${media_basename}" ]
         then
-          echo_error "The \"media_basename\" variable is missing or is not a directory."
+          echo_error "The \"media_basename\" variable is missing ."
         fi
       ;;
       media_ffprobe)