Fix/metar reading (#354)

* Account for empty ICAO; added tests

* Fix null returns

* Fix typo in volume units display

* Add version field for bug report template

* Some more changes to the bug report template

app/Services/AirportService.php

@@ -26,16 +26,16 @@ class AirportService extends Service
      *
      * @return Metar|null
      */
-    public function getMetar($icao): Metar
+    public function getMetar($icao)
     {
-        $metar = null;
-        $wind = null;
-        $raw_metar = $this->metarProvider->get_metar($icao);
+        $icao = trim($icao);
+        if ($icao === '') {
+            return;
+        }
 
+        $raw_metar = $this->metarProvider->get_metar($icao);
         if ($raw_metar && $raw_metar !== '') {
             return new Metar($raw_metar);
         }
-
-        return null;
     }
 }

app/Services/Metar/AviationWeather.php

@@ -35,6 +35,10 @@ class AviationWeather extends Metar
      */
     protected function metar($icao): string
     {
+        if ($icao === '') {
+            return '';
+        }
+
         $url = static::METAR_URL.$icao;
 
         try {