Fix contrib/seed.sh script

`jo -a` is waiting on stdin; adding `< /dev/null` allows to
generate an empty array without waiting on stdin.D

Signed-off-by: Ludovic Vielle <ludovic@probo.com>

contrib/seed.sh

@@ -26,7 +26,6 @@ FULL_NAME="Seed Admin"
 ORG_NAME="Acme Corp"
 
 # Helpers
-
 gql_connect() {
   local query="$1"
   local variables="${2:-"{}"}"
@@ -60,6 +59,9 @@ prb_api() {
   echo "$resp"
 }
 
+curl -sf -o /dev/null "$BASE_URL/healthz" \
+  || { echo "ERROR: API at $BASE_URL is not available" >&2; exit 1; }
+
 echo "==> Bootstrapping user and organization..."
 vars=$(jo input="$(jo \
   email="$EMAIL" \
@@ -144,7 +146,7 @@ create_person() {
     fullName="$full_name" \
     role=EMPLOYEE \
     kind=EMPLOYEE \
-    additionalEmailAddresses="$(jo -a)" \
+    additionalEmailAddresses="$(jo -a < /dev/null)" \
     position="$position" \
   )")
   resp=$(gql_connect '