Fixes #2923 when using EncryptPreparedStatement to savebatch occours error

[xiyelife]

Fixes #ISSUSE_ID.

Changes proposed in this pull request:
fix the mybatis setQueryTimeout() NPE

[coveralls]

Pull Request Test Coverage Report for Build 290

• 2 of 4 (50.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.007%) to 64.945%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
sharding-jdbc/sharding-jdbc-core/src/main/java/org/apache/shardingsphere/shardingjdbc/jdbc/core/statement/EncryptPreparedStatement.java	2	4	50.0%

Totals
Change from base Build 315:	-0.007%
Covered Lines:	9217
Relevant Lines:	14192

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💛 - Coveralls

[tristaZero]

@xiyelife Hi, thanks for your pr, but can you tell me why you add this judgement of null == encryptStatment? Is there any scenario?

[xiyelife]

as the issue says: #2923 (comment)
when mybatis prepare the statement, it will set the queryTimeout ,but the preparedStatement does not created at this time, and the NPE occured

[tristaZero]

@xiyelife Got it, but if mybatis prepares a statement, the fisrt thing it should do is to create a statement, is't right? Can you debug your program and check whether mybatis creates an EncryptPreparedStatement?