Ensure pi-gens Wi-Fi variables are unset if not provided, it tries to…

… use blank values too.

config

@@ -7,10 +7,6 @@ export FIRST_USER_NAME=${FIRST_USER:=pi}
 export FIRST_USER_PASS=${FIRST_USERPASS:=rasberry}
 export ENABLE_SSH=${SSH_ENABLED:=1}
 
-export WPA_ESSID=${WPA_SSID:=""}
-export WPA_PASSWORD=${WPA_PASSPHRASE:=""}
-export WPA_COUNTRY=${WPA_COUNTRY:=""}
-
 export LOCALE_DEFAULT=${LOCALE:=$(localectl status | sed -n -e 's/^.*LANG=//p')}
 export KEYBOARD_KEYMAP=${KEYMAP:=$(localectl status | sed -n -e 's/^.*X11 Layout: //p')}
 export KEYBOARD_LAYOUT=${KEY_LAYOUT:=$(debconf-show keyboard-configuration | sed -n -e 's/^.*keyboard-configuration\/layout: //p')}
@@ -22,4 +18,18 @@ export DOCKER_ADDL_MOUNTS=(
     "${CONFIG_DIR}/bootstrap-resources:/bootstrap-resources:ro")
 
 # We only want to build a lite image
-export STAGE_LIST="stage0 stage1 stage2"
+export STAGE_LIST="stage0 stage1 stage2"
+
+# Set up WiFi
+if [[ -z $WPA_SSID || -z $WPA_PASSPHRASE || -z $WPA_COUNTRY ]]
+then
+    echo "Skipping Wi-Fi setup, one or more required Wi-Fi fields were not provided"
+    unset WPA_ESSID
+    unset WPA_PASSWORD
+    unset WPA_COUNTRY
+else
+    echo "Setting up Wi-Fi, step 1/2..."
+    export WPA_ESSID="${WPA_SSID}"
+    export WPA_PASSWORD="${WPA_PASSPHRASE}"
+    export WPA_COUNTRY="${WPA_COUNTRY}"
+fi