Return audit results on empty Regexp

In addition to nil objects

Author: Ang Ming Yi

lib/rules/rule_auditor.rb

@@ -162,7 +162,7 @@ def audit_commit_pattern(commit, pattern, diff)
 
   def audit_specific_file_changes_pattern(pattern, filename, diff)
     results = []
-    return nil if filename.blank? || diff.blank?
+    return nil if filename.blank? || filename == // || diff.blank?
     diff.each do |d|
       next if d.file.empty? || (d.file =~ filename).blank?
       next if d.body.empty? || (d.body =~ pattern).blank?