Fix an error when the unit does not have a rate of fire

www/res/scripts/calculations.php

@@ -69,7 +69,9 @@ function calculateDps($stdClassWeapon, $unitID, $Projectile){
         //    but thats pretty much a bug so not taken into account here
 
         ///  BTW - SpookyDB uses round(), not floor(), based on the values seen there.  Values will not match between DBs.  floor() is the correct method.
-        $trueReload = max(0.1*floor(10 / $weapon["RateOfFire"]), 0.1); 
+        if(isset($weapon["RateOfFire"])) {
+            $trueReload = max(0.1*floor(10 / $weapon["RateOfFire"]), 0.1);
+        }
         $trueReload = max(
                 ($weapon["RackSalvoChargeTime"] ?? 0) + ($weapon["RackSalvoReloadTime"] ?? 0) + 
                     ($weapon["MuzzleSalvoDelay"] ?? 0)*(($weapon["MuzzleSalvoSize"] ?? 1)-1),