fix side table join error msg

Author: a49a

.gitignore

@@ -8,6 +8,7 @@ target/
 *.eclipse.*
 *.iml
 plugins/
+sqlplugins/
 lib/
 .vertx/
 .DS_Store

core/src/main/java/com/dtstack/flink/sql/side/BaseSideInfo.java

@@ -162,7 +162,7 @@ public void dealOneEqualCon(SqlNode sqlNode, String sideTableName){
                 }
             }
             if(equalFieldIndex == -1){
-                throw new RuntimeException("can't find equal field " + rightField);
+                throw new RuntimeException("can't find equal field " + leftField);
             }
 
             equalValIndex.add(equalFieldIndex);