[gha] Handle missing fields in hyperjump labels

Apparently GHA auto-removes empty inputs so even though they are specified
they don't make it to the action. To work around this we make the fields
optional and handle the case where they are empty.

Closes: diem#5412
Approved by: bmwill

.github/actions/hyperjump-labels/action.yml

@@ -9,10 +9,10 @@ inputs:
     required: true
   add:
     description: label strings to add
-    required: true
+    required: false
   remove:
     description: label strings to remove
-    required: true
+    required: false
 runs:
   using: 'node12'
   main: 'dist/index.js'

.github/actions/hyperjump-labels/src/index.js

@@ -5,8 +5,8 @@ async function main() {
   try {
     const github_token = core.getInput("github-token", {required: true});
     const number = core.getInput("number", {required: true});
-    const add_labels = core.getInput("add", {required: true});
-    const remove_labels = core.getInput("remove", {required: true});
+    const add_labels = core.getInput("add", {required: false});
+    const remove_labels = core.getInput("remove", {required: false});
 
     if (!add_labels && !remove_labels) {
       core.warning("add and remove fields both empty");