Do not fail script when PR body is empty

index.js

@@ -92,7 +92,9 @@ const extractTrelloCardIds = (prBody, stopOnNonLink = true) =>   {
 
   const cardIds = [];
   const lines = prBody.split(browserEol);
-
+  if(!prBody || prBody==="") {
+    return cardIds;
+  }
   //loop and gather up cardIds, skipping blank lines. stopOnNonLink == true will bust out when we're out of link-only territory.
   for(const line of lines) {
     const matches = linkRegex.exec(line);
@@ -168,4 +170,4 @@ const buildTrelloLinkComment = async (cardId) => {
     //failure will stop PR from being mergeable if that setting enabled on the repo.  there is not currently a neutral exit in actions v2.
     core.setFailed(error.message);
   }
-})();
+})();