Fix edge case in shellshock where a victim with no attackable URLs returned None

chaos_monkey/exploit/shellshock.py

@@ -144,6 +144,8 @@ class ShellShockExploiter(HostExploiter):
 
             return True
 
+        return False
+
     @classmethod
     def check_remote_file_exists(cls, url, header, exploit, file_path):
         """