feat(CONTRIBUTING.md): update CONTRIBUTING.md

1. update image links
2. modify log level

Author: forfreeday

CONTRIBUTING.md

@@ -103,12 +103,12 @@ If you want to contribute codes to java-tron, please follow the following steps:
 
   Submit a pull request (PR) from your repository to `tronprotocol/java-tron`.
   Please be sure to click on the link in the red box shown below. Select the base branch for tronprotocol and the compare branch for your personal fork repository.
-  ![](https://codimd.s3.shivering-isles.com/demo/uploads/e24435ab42e4287d9369a2136.png)
+  ![image](https://raw.githubusercontent.com/tronprotocol/documentation-en/master/images/javatron_pr.png)
 
 
 
 ## Code Review Guidelines
-The only way to get code into java-tron is to send a pull request. Those pull requests need to be reviewed by someone. there a guide that explains our expectations around PRs for both authors and reviewers.
+The only way to get code into java-tron is to send a pull request. Those pull requests need to be reviewed by someone. The following guide explains our expectations around PRs for both authors and reviewers.
 
 ### Terminology
 - The author of a pull request is the entity who wrote the diff and submitted it to GitHub.

framework/src/main/java/org/tron/core/Wallet.java

@@ -687,7 +687,7 @@ public long getTransactionCountByBlockNum(long blockNum) {
       Block block = chainBaseManager.getBlockByNum(blockNum).getInstance();
       count = block.getTransactionsCount();
     } catch (StoreException e) {
-      logger.error(e.getMessage());
+      logger.warn(e.getMessage());
     }
 
     return count;
@@ -1414,7 +1414,7 @@ public Block getBlockById(ByteString blockId) {
     try {
       block = chainBaseManager.getBlockStore().get(blockId.toByteArray()).getInstance();
     } catch (StoreException e) {
-      logger.error(e.getMessage());
+      logger.warn(e.getMessage());
     }
     return block;
   }