Add test for METAR string

PR aims to fix the bug #1071 by checking both the wind speed and it's value for starting Wind Chill calculation.

app/Support/Metar.php

@@ -1772,7 +1772,7 @@ class Metar implements \ArrayAccess
      */
     private function calculate_wind_chill($temperature_f): void
     {
-        if ($temperature_f < 51 && $this->result['wind_speed'] !== 0) {
+        if ($temperature_f < 51 && $this->result['wind_speed'] && $this->result['wind_speed'] !== 0) {
             $windspeed = $this->result['wind_speed']->toUnit('mph');
             if ($windspeed > 3) {
                 $chill_f = 35.74 + 0.6215 * $temperature_f - 35.75 * ($windspeed ** 0.16);

tests/MetarTest.php

@@ -151,6 +151,19 @@ class MetarTest extends TestCase
         $this->assertEquals('Few at 1500 feet; few at 25000 feet', $metar['clouds_report_ft']);
     }
 
+    /**
+     * https://github.com/nabeelio/phpvms/issues/1071
+     */
+    public function testMetarWindSpeedChill()
+    {
+        $metar = 'EKYT 091020Z /////KT CAVOK 02/M03 Q1019';
+        $metar = Metar::parse($metar);
+
+        $this->assertEquals('VFR', $metar['category']);
+        $this->assertNull($metar['wind_speed']);
+        $this->assertEquals(6.21, $metar['visibility']['mi']);
+    }
+
     /**
      * Visibility in KM not parsed
      *