Fix an issue where info would raise an exception

Fix instances where the `info` command would raise an exception while
generating the payload to calculate its length.

lib/msf/core/payload/adapter/fetch.rb

@@ -7,7 +7,8 @@ def initialize(*args)
         Msf::OptBool.new('FETCH_DELETE', [true, 'Attempt to delete the binary after execution', false]),
         Msf::OptString.new('FETCH_FILENAME', [ false, 'Name to use on remote system when storing payload; cannot contain spaces or slashes', Rex::Text.rand_text_alpha(rand(8..12))], regex: /^[^\s\/\\]*$/),
         Msf::OptPort.new('FETCH_SRVPORT', [true, 'Local port to use for serving payload', 8080]),
-        Msf::OptAddressRoutable.new('FETCH_SRVHOST', [ false, 'Local IP to use for serving payload']),
+        # FETCH_SRVHOST defaults to LHOST, but if the payload doesn't connect back to Metasploit (e.g. adduser, messagebox, etc.) then FETCH_SRVHOST needs to be set
+        Msf::OptAddressRoutable.new('FETCH_SRVHOST', [ !options['LHOST']&.required, 'Local IP to use for serving payload']),
         Msf::OptString.new('FETCH_URIPATH', [ false, 'Local URI to use for serving payload', '']),
         Msf::OptString.new('FETCH_WRITABLE_DIR', [ true, 'Remote writable dir to store payload; cannot contain spaces', ''], regex:/^[\S]*$/)
       ]
@@ -80,8 +81,6 @@ def fetch_bindnetloc
   end
 
   def generate(opts = {})
-    datastore['FETCH_SRVHOST'] = datastore['LHOST'] if datastore['FETCH_SRVHOST'].blank?
-    fail_with(Msf::Module::Failure::BadConfig, 'FETCH_SRVHOST required') if datastore['FETCH_SRVHOST'].blank?
     opts[:arch] ||= module_info['AdaptedArch']
     opts[:code] = super
     @srvexe = generate_payload_exe(opts)
@@ -128,7 +127,10 @@ def handle_connection(conn, opts = {})
   end
 
   def srvhost
-    datastore['FETCH_SRVHOST']
+    host = datastore['FETCH_SRVHOST']
+    host = datastore['LHOST'] if host.blank?
+    host = '127.127.127.127' if host.blank?
+    host
   end
 
   def srvnetloc