fix invalid syntax in old zsh versions

themes/agnoster.zsh-theme

@@ -212,7 +212,7 @@ prompt_virtualenv() {
 # - am I root
 # - are there background jobs?
 prompt_status() {
-  local -a symbols=()
+  local -a symbols
 
   [[ $RETVAL -ne 0 ]] && symbols+="%{%F{red}%}✘"
   [[ $UID -eq 0 ]] && symbols+="%{%F{yellow}%}⚡"