Merge pull request #736 from tronprotocol/feature/add_verification_for_freezeAsset

add long overflow verification

Author: nanfengpo

src/main/java/org/tron/core/actuator/AssetIssueActuator.java

@@ -163,6 +163,9 @@ public boolean validate() throws ContractValidateException {
 
       while (iterator.hasNext()) {
         FrozenSupply next = iterator.next();
+        if (next.getFrozenAmount() <= 0) {
+          throw new ContractValidateException("Frozen supply must be greater than 0!");
+        }
         if (next.getFrozenAmount() > remainSupply) {
           throw new ContractValidateException("Frozen supply cannot exceed total supply");
         }