ignore non-interesting errors when processing metadata

lib/metadata.js

@@ -195,6 +195,10 @@ Meta.createLineHandler = function (ref, errorHandler) {
 
     return function (err, line) {
         if (err) {
+            // it's not abnormal that metadata exists without a corresponding log
+            // so ENOENT is fine
+            if (ref.index === 0 && err.code === 'ENOENT') { return; }
+            // any other errors are abnormal
             return void errorHandler('METADATA_HANDLER_LINE_ERR', {
                 error: err,
                 index: ref.index,