fix: suppress empty versionScheme warnings

lib/versioning/index.js

@@ -7,9 +7,13 @@ const schemes = {
 };
 
 module.exports = function getVersionScheme(versionScheme) {
+  if (!versionScheme) {
+    logger.debug('Missing versionScheme');
+    return semver;
+  }
   const scheme = schemes[versionScheme];
   if (!scheme) {
-    logger.warn({ versionScheme }, 'Unknown verion scheme');
+    logger.warn({ versionScheme }, 'Unknown version scheme');
     return semver;
   }
   return scheme;