search: fixed output error when no results found.

src/Composer/Command/SearchCommand.php

@@ -67,10 +67,12 @@ EOT
         $this->output = $output;
         $repos->filterPackages(array($this, 'processPackage'), 'Composer\Package\CompletePackage');
 
+        if (!empty($this->lowMatches)) {
             foreach ($this->lowMatches as $details) {
                 $output->writeln($details['name'] . '<comment>:</comment> '. $details['description']);
             }
         }
+    }
 
     public function processPackage($package)
     {