added configurable string when there is no IP

powerlevel9k.zsh-theme

@@ -429,6 +429,7 @@ prompt_battery() {
 prompt_public_ip() {
   # set default values for segment
   set_default POWERLEVEL9K_PUBLIC_IP_TIMOUT "300"
+  set_default POWERLEVEL9K_PUBLIC_IP_NONE ""
   set_default POWERLEVEL9K_PUBLIC_IP_FILE "/tmp/p9k_public_ip"
   set_default POWERLEVEL9K_PUBLIC_IP_HOST "http://ident.me"
 
@@ -440,7 +441,7 @@ prompt_public_ip() {
     timediff=$(($(date +%s) - $(date -r $POWERLEVEL9K_PUBLIC_IP_FILE +%s)))
     [[ $timediff -gt $POWERLEVEL9K_PUBLIC_IP_TIMOUT ]] && refresh_ip=true
     # If tmp file is empty get a fresh IP
-    [[ -z $(cat $POWERLEVEL9K_PUBLIC_IP_FILE) ]] && refresh_ip=true
+    [[ -z $(cat $POWERLEVEL9K_PUBLIC_IP_FILE) || $(cat $POWERLEVEL9K_PUBLIC_IP_FILE) =~ $POWERLEVEL9K_PUBLIC_IP_NONE ]] && refresh_ip=true
   else
     touch $POWERLEVEL9K_PUBLIC_IP_FILE && refresh_ip=true
   fi
@@ -461,7 +462,7 @@ prompt_public_ip() {
     fi
 
     # write IP to tmp file or clear tmp file if an IP was not retrieved
-    [[ -n $fresh_ip ]] && echo $fresh_ip > $POWERLEVEL9K_PUBLIC_IP_FILE || echo "" > $POWERLEVEL9K_PUBLIC_IP_FILE
+    [[ -n $fresh_ip ]] && echo $fresh_ip > $POWERLEVEL9K_PUBLIC_IP_FILE || echo $POWERLEVEL9K_PUBLIC_IP_NONE > $POWERLEVEL9K_PUBLIC_IP_FILE
   fi
 
   # read public IP saved to tmp file