Don't publish release if github keys aren't set (#364)

Co-authored-by: Will <[email protected]>

.travis.yml

@@ -45,4 +45,9 @@ jobs:
         - crystal spec -v || travis_terminate 1;
         - docker pull crystallang/crystal:0.35.1-alpine
         - docker run --rm -it -v $PWD:/workspace -w /workspace crystallang/crystal:0.35.1-alpine crystal build src/cnf-conformance.cr --release --static --link-flags "-lxml2 -llzma"
-        - ./cnf-conformance upsert_release
+        - |
+          if [ -z "${GITHUB_USER+x}" ] || [ -z "${GITHUB_TOKEN+x}" ]; then
+            exit 0
+          else
+            ./cnf-conformance upsert_release
+          fi