<fix>[kvm]: fix invalid edk version tag error

Related: ZSV-11310

Change-Id: I737178716776676c766e7164736b6679756c7065

Author: Zhang Wenhao

plugin/kvm/src/main/java/org/zstack/kvm/BootKvmStartVmExtension.java

@@ -1,5 +1,6 @@
 package org.zstack.kvm;
 
+import org.apache.commons.lang.StringUtils;
 import org.zstack.compute.vm.VmSystemTags;
 import org.zstack.header.errorcode.ErrorCode;
 import org.zstack.header.vm.VmInstanceInventory;
@@ -47,7 +48,7 @@ public void afterReceiveVmDeviceInfoResponse(VmInstanceInventory vm, KVMAgentCom
 
     @SuppressWarnings("unchecked")
     private void saveVmEdkStatesFromCommand(String vmUuid, KVMAgentCommands.VmDevicesInfoResponse rsp) {
-        if (rsp.getEdkRpm() == null) {
+        if (StringUtils.isEmpty(rsp.getEdkRpm())) {
             VM_EDK.deleteInherentTag(vmUuid);
             return;
         }