[BugFix] 使用字符串类型注入 key 之前加上类型检查，避免类型不匹配导致注入失败。

mybatis-plus-core/src/main/java/com/baomidou/mybatisplus/core/MybatisParameterHandler.java

@@ -146,8 +146,10 @@ public class MybatisParameterHandler implements ParameterHandler {
                         } else {
                             throw new MybatisPlusException("Key type '" + keyType + "' not supported");
                         }
-                    } else {
+                    } else if (String.class.isAssignableFrom(keyType)) {
                         metaObject.setValue(keyProperty, identifierGenerator.nextId(entity).toString());
+                    } else {
+                        metaObject.setValue(keyProperty, identifierGenerator.nextId(entity));
                     }
                 } else if (idType.getKey() == IdType.ASSIGN_UUID.getKey()) {
                     metaObject.setValue(keyProperty, identifierGenerator.nextUUID(entity));