typo

Author: David Maloney

modules/exploits/windows/winrm/winrm_powershell.rb

@@ -67,7 +67,7 @@ def check
 		if streams['stdout'].include? 'Unrestricted'
 			return Msf::Exploit::CheckCode::Vulnerable
 		else
-			unless streams['stderr'] = ''
+			unless streams['stderr'] == ''
 				print_error streams['stderr']
 			end
 			return Msf::Exploit::CheckCode::Safe