Fix check of setEnvironmentProduction setting

Author: niallzato

Sources/SegmentAdjust/AdjustDestination.swift

@@ -56,7 +56,7 @@ open class AdjustDestination: NSObject, DestinationPlugin {
         adjustSettings = settings
 
         var environment = ADJEnvironmentSandbox
-        if let _ = settings.setEnvironmentProduction {
+        if let isProduction = settings.setEnvironmentProduction, isProduction == true {
             environment = ADJEnvironmentProduction
         }