Update 1.0 to 1.2

[Mutineer]

sudo systemctl enable hostapd.service

then update
you need to update with an ethernet connection or a tethered phone , the wifi is being updated and you will lose connection if you try updating over wifi

Ran your script, rebooted and tried to upgrade OP, still get this error.
PI is on Ethernet, and wifi turned off.
I've even tried on a fresh new SD card, and complete new install.

After this operation, 0 B of additional disk space will be used.
Setting up hostapd (2:2.6-21~bpo9~rpt1) ...
Job for hostapd.service failed because the control process exited with error code.
See "systemctl status hostapd.service" and "journalctl -xe" for details.
invoke-rc.d: initscript hostapd, action "restart" failed.
* hostapd.service - Advanced IEEE 802.11 AP and IEEE 802.1X/WPA/WPA2/EAP Authenticator
   Loaded: loaded (/lib/systemd/system/hostapd.service; enabled; vendor preset: enabled)
   Active: activating (auto-restart) (Result: exit-code) since Sat 2019-08-31 19:22:56 AEST; 46ms ago
  Process: 4242 ExecStart=/usr/sbin/hostapd -P /run/hostapd.pid -B $DAEMON_OPTS ${DAEMON_CONF} (code=exited, status=1/FAILURE)

Aug 31 19:22:56 openplotter systemd[1]: hostapd.service: Control process exi…s=1
Aug 31 19:22:56 openplotter systemd[1]: Failed to start Advanced IEEE 802.11…or.
Aug 31 19:22:56 openplotter systemd[1]: hostapd.service: Unit entered failed…te.
Aug 31 19:22:56 openplotter systemd[1]: hostapd.service: Failed with result …e'.
Hint: Some lines were ellipsized, use -l to show in full.
dpkg: error processing package hostapd (--configure):
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 hostapd
E: Sub-process /usr/bin/dpkg returned an error code (1)