Avoid divide-by-zero fatal error

Author: fredden

app/code/Magento/Cron/Model/Schedule.php

@@ -215,7 +215,7 @@ public function matchCronExpression($expr, $num)
             $to = $from;
         }
 
-        if ($from === false || $to === false) {
+        if ($from === false || $to === false || $mod == 0) {
             throw new CronException(__('Invalid cron expression: %1', $expr));
         }
 

app/code/Magento/Cron/Test/Unit/Model/ScheduleTest.php

@@ -426,6 +426,7 @@ public function matchCronExpressionExceptionDataProvider(): array
             ['1/'],       //Invalid cron expression, expecting numeric modulus: 1/
             ['-'],        //Invalid cron expression
             ['1-2-3'],    //Invalid cron expression, expecting 'from-to' structure: 1-2-3
+            ['0/0'],
         ];
     }