Fix IndexOutOfBoundsException when creating basic network (#4464)

For Basic network isolation methods are not provided, and exception is
thrown when trying to encode the Vlan id. That's why we have to check
before encoding that the list with isolation methods is not empty

Author: slavkap

engine/orchestration/src/main/java/org/apache/cloudstack/engine/orchestration/NetworkOrchestrator.java

@@ -2484,7 +2484,7 @@ protected URI encodeVlanIdIntoBroadcastUri(String vlanId, PhysicalNetwork pNtwk)
             throw new InvalidParameterValueException(String.format("Failed to encode VLAN/VXLAN %s into a Broadcast URI. Physical Network cannot be null.", vlanId));
         }
 
-        if(StringUtils.isNotBlank(pNtwk.getIsolationMethods().get(0))) {
+        if(!pNtwk.getIsolationMethods().isEmpty() && StringUtils.isNotBlank(pNtwk.getIsolationMethods().get(0))) {
             String isolationMethod = pNtwk.getIsolationMethods().get(0).toLowerCase();
             String vxlan = BroadcastDomainType.Vxlan.toString().toLowerCase();
             if(isolationMethod.equals(vxlan)) {