prompt: fix usage of zsh-async in sorin prompt (#1810)

modules/prompt/functions/prompt_sorin_setup

@@ -54,6 +54,13 @@ function prompt_sorin_async_callback {
         zle && zle reset-prompt
       fi
       ;;
+    "[async]")
+      # Code is 1 for corrupted worker output and 2 for dead worker.
+      if [[ $2 -eq 2 ]]; then
+	  # Our worker died unexpectedly.
+          typeset -g prompt_prezto_async_init=0
+      fi
+      ;;
   esac
 }