Check if wifi adaptors exist

src/freedombone-controlpanel

@@ -1720,6 +1720,12 @@ function wifi_enable {
 }
 
 function menu_wifi {
+    if [[ "$(wifi_exists)" == "0" ]]; then
+        dialog --title $"Wifi" \
+               --msgbox $"No wifi adaptors were detected" 6 40
+        return
+    fi
+
     while true
     do
         status_str=$'Wifi OFF'

src/freedombone-utils-wifi

@@ -573,6 +573,14 @@ function count_wlan {
     echo $ctr
 }
 
+function wifi_exists {
+    if grep -q "wlan" /proc/net/dev; then
+        echo "1"
+    else
+        echo "0"
+    fi
+}
+
 function remove_wifi_startup_script {
     remove_config_param "WIFI_INTERFACE"
     systemd_file=/etc/systemd/system/wifistart.service