Test whether filename is empty during pre-create hook

.hooks/pre-create

@@ -1,8 +1,7 @@
 #!/bin/bash
 
 filename=$(cat /dev/stdin | jq .MetaData.filename)
-
-if [ -n "$filename" ]; then
+if [ -z "$filename" ]; then
   echo "Error: no filename provided"
   exit 1
 fi