Do not print empty built-in reports

- This avoid irregular breaks in the console logs for successful but empty report formats (like text and compact). XML reports would print as XML syntax requires root tags

Author: abhishekdev

index.js

@@ -96,15 +96,15 @@ cssLintPlugin.reporter = function(customReporter) {
   }
 
   if (builtInReporter) {
-    output = reporter.startFormat();
+    output = [reporter.startFormat()];
   }
 
   return through.obj(
     function(file, enc, cb) {
       // Only report if CSSLint was ran and errors were found
       if (file.csslint && !file.csslint.success) {
         if (builtInReporter) {
-          output += reporter.formatResults(file.csslint.originalReport, file.path);
+          output.push(reporter.formatResults(file.csslint.originalReport, file.path));
         }
         else {
           reporter(file);
@@ -114,10 +114,14 @@ cssLintPlugin.reporter = function(customReporter) {
       return cb(null, file);
     },
     function(cb) {
+      var report;
+
       if (builtInReporter) {
-        output += reporter.endFormat();
+        output.push(reporter.endFormat());
+        report = output.join('');
 
-        gutil.log(output);
+        // Only print report if the report is not empty
+        report && gutil.log(report);
       }
 
       return cb();