dbus Method “SignalPoll” is returning incorrect type

[Adam Fairbrother]

The SignalPoll method should return a 'a{sv}' type as shown by introspection:

    $ gdbus introspect -y -d fi.w1.wpa_supplicant1 -o /fi/w1/wpa_supplicant1/Interfaces/0 | grep SignalPoll
      SignalPoll(out a{sv} args);

instead a 'v' type is returned:

    $ gdbus call -y -d fi.w1.wpa_supplicant1 -o /fi/w1/wpa_supplicant1/Interfaces/0 -m fi.w1.wpa_supplicant1.Interface.SignalPoll
(<{'rssi': <-64>, 'linkspeed': <24>, 'noise': <9999>, 'frequency': <uint32 5260>, 'width': <'40 MHz'>}>,)

Description: Ubuntu 20.04 LTS
Release: 20.04

wpasupplicant:
  Installed: 2:2.9-1ubuntu4.1
  Candidate: 2:2.9-1ubuntu4.1
  Version table:
 *** 2:2.9-1ubuntu4.1 500
        500 http://ports.ubuntu.com/ubuntu-ports focal-updates/main arm64 Packages
        100 /var/lib/dpkg/status
     2:2.9-1ubuntu4 500
        500 http://ports.ubuntu.com/ubuntu-ports focal/main arm64 Packages