fix bug

src/connector/jdbc/src/main/java/com/taosdata/jdbc/TSDBPreparedStatement.java

@@ -61,10 +61,12 @@ public class TSDBPreparedStatement extends TSDBStatement implements PreparedStat
             this.isPrepared = true;
         }
 
+		if (parameterCnt > 1) {
 	        // the table name is also a parameter, so ignore it.
 	        this.colData = new ArrayList<ColumnInfo>(parameterCnt - 1);
 	        this.colData.addAll(Collections.nCopies(parameterCnt - 1, null));
 		}
+    }
 
     private void init(String sql) {
         this.rawSql = sql;