make getTimeZoneId non-optional

Author: emawby

OneSignalSDK/onesignal/core/src/main/java/com/onesignal/common/TimeUtils.kt

@@ -17,7 +17,7 @@ object TimeUtils {
         return offset / 1000
     }
 
-    fun getTimeZoneId(): String? {
+    fun getTimeZoneId(): String {
         return if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
             ZoneId.systemDefault().id
         } else {

OneSignalSDK/onesignal/core/src/main/java/com/onesignal/user/internal/operations/impl/executors/LoginUserOperationExecutor.kt

@@ -94,7 +94,7 @@ internal class LoginUserOperationExecutor(
         var identities = mapOf<String, String>()
         var subscriptions = mapOf<String, SubscriptionObject>()
         val properties = mutableMapOf<String, String>()
-        properties["timezone_id"] = TimeUtils.getTimeZoneId()!!
+        properties["timezone_id"] = TimeUtils.getTimeZoneId()
 
         if (createUserOperation.externalId != null) {
             val mutableIdentities = identities.toMutableMap()