DNS feature stops working when trying to use it before enabling the feature

[cdelafuente-r7]

The DNS feature stops working when the dns_feature value is set to false or if it is not present in the config, when trying to use the dns command.

To reproduce this bug:

1. start msfconsole without a config file in $HOME/.msf4/
2. run dns help and see the expected error message
3. enable the feature with features set dns_feature true
4. run dns help again and nothing happens

msf6 > ls -l ~/.msf4/config
[*] exec: ls -l ~/.msf4/config

ls: /home/msfuser/.msf4/config: No such file or directory
msf6 > dns help
[-] Unknown command: dns. Run the help command for more details.
msf6 > features set dns_feature true
dns_feature => true
msf6 > dns help
msf6 > dns print
msf6 >

Other scenario:

1. start msfconsole
2. disable the feature with features set dns_feature false
3. exit and restart msfconsole
4. run dns help and see the expected error message
5. enable the feature with features set dns_feature true
6. run dns help again and nothing happens

msf6 > features set dns_feature false
dns_feature => false
msf6 > save
Saved configuration to: /home/msfuser/.msf4/config
msf6 > exit
❯ ./msfconsole -q
msf6 > cat ~/.msf4/config
[*] exec: cat ~/.msf4/config

[framework/core]

[framework/features]
dns_feature=false

[framework/ui/console]

msf6 > dns help
[-] Unknown command: dns. Run the help command for more details.
msf6 > features set dns_feature true
dns_feature => true
msf6 > dns help
msf6 >

This doesn't happen if the dns feature is enabled in the config.

msf6 > cat ~/.msf4/config
[*] exec: cat ~/.msf4/config

[framework/core]

[framework/features]
dns_feature=true

[framework/ui/console]

msf6 > features set dns_feature false
dns_feature => false
msf6 > dns help
[-] Unknown command: dns. Run the help command for more details.
msf6 > features set dns_feature true
dns_feature => true
msf6 > dns help
Manage Metasploit's DNS resolution behaviour

USAGE:
  dns [add] [--index <insertion index>] [--rule <wildcard DNS entry>] [--session <session id>] <resolver> ...
  dns [add-static] <hostname> <IP address> ...
  dns [remove/del] -i <entry id> [-i <entry id> ...]
  dns [remove-static] <hostname> [<IP address> ...]
  dns [flush-cache]
  dns [flush-entries]
  dns [flush-static]
  dns [print]
  dns [reset-config] [-y/--yes] [--system]
  dns [resolve] [-f <address family>] <hostname> ...
  dns [help] [subcommand]

SUBCOMMANDS:
  add           - Add a DNS resolution entry to resolve certain domain names through a particular DNS resolver
  add-static    - Add a statically defined hostname
  flush-cache   - Remove all cached DNS answers
  flush-entries - Remove all configured DNS resolution entries
  flush-static  - Remove all statically defined hostnames
  print         - Show all configured DNS resolution entries
  remove        - Delete a DNS resolution entry
  remove-static - Delete a statically defined hostname
  reset-config  - Reset the DNS configuration
  resolve       - Resolve a hostname

EXAMPLES:
  Display help information for the 'add' subcommand
    dns help add

msf6 >