resilient: promises shouldn't fail until 1st backup is done

stack/resilient/buildout.cfg

@@ -59,7 +59,7 @@ mode = 0644
 recipe = slapos.recipe.template
 url = ${:_profile_base_location_}/pbsready-export.cfg.in
 output = ${buildout:directory}/pbsready-export.cfg
-md5sum = bf7f6b35b54ac10988cbbd4439e1391b
+md5sum = 48cf26431ab052eae8227efd457db8c3
 mode = 0644
 
 [template-pull-backup]

stack/resilient/pbsready-export.cfg.in

@@ -65,7 +65,9 @@ template = inline:
   #!${bash:location}/bin/bash
   EXPORTER_FEED="$${notifier-exporter:log-file}"
   FAILURE_PATTERN="FAILURE"
-  tail -n 1 $EXPORTER_FEED | grep -vq FAILURE_PATTERN
+  if [ -s "$EXPORTER_FEED" ]; then
+    tail -n 1 $EXPORTER_FEED | grep -vq FAILURE_PATTERN
+  fi
 rendered = $${basedirectory:promises}/exporter-status
 
 [cron-entry-backup]