Fix handling null query bindings

Author: txase

index.js

@@ -160,7 +160,12 @@ class Client_AuroraDataMySQL extends Client_MySQL { // eslint-disable-line camel
       }
 
       if (value === null) {
-        return null;
+        return {
+          name,
+          value: {
+            isNull: true
+          }
+        };
       }
 
       if (Buffer.isBuffer(value) || ArrayBuffer.isView(value)) {

tests/test.js

@@ -210,7 +210,12 @@ describe('Query statement tests', () => {
             stringValue: '2020-01-01 00:00:00.000'
           }
         },
-        null
+        {
+          name: '6',
+          value: {
+            isNull: true
+          }
+        }
       ],
       includeResultMetadata: true
     });