Fix metar parsing issue

app/Support/Metar.php

@@ -993,7 +993,7 @@ class Metar implements \ArrayAccess
                 $observed['amount'] = $found[2];
             }
         } // Cloud cover observed
-        elseif (isset($found[5]) && !empty($found[5])) {
+        elseif (isset($found[5]) && !empty($found[5]) && is_numeric($found[5])) {
             $observed['height'] = new Altitude($found[5] * 100, 'feet');
 
             // Cloud height

tests/MetarTest.php

@@ -82,6 +82,8 @@ class MetarTest extends TestCase
     {
         $metar = 'EGLL 261250Z AUTO 17014KT 8000 -RA BKN010/// '
                 .'BKN016/// OVC040/// //////TCU 13/12 Q1008 TEMPO 4000 RA';
+
+        $parsed = Metar::parse($metar);
     }
 
     public function testMetarTrends()