fixed issue #220

[coveralls]

Pull Request Test Coverage Report for Build 741

• 1 of 7 (14.29%) changed or added relevant lines in 2 files are covered.
• 79 unchanged lines in 10 files lost coverage.
• Overall coverage increased (+7.6%) to 82.572%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/main/java/seedu/address/logic/parser/FindCommandParser.java	1	3	33.33%
src/main/java/seedu/address/logic/parser/SortCommandParser.java	0	4	0.0%
<!--	Total:	1	7	14.29%	-->

Files with Coverage Reduction	New Missed Lines	%
src/main/java/seedu/address/logic/parser/EditHistCommandParser.java	1	88.46%
src/main/java/seedu/address/model/person/addinfo/Nric.java	2	93.1%
src/main/java/seedu/address/commons/util/SecretKeyUtil.java	3	53.85%
src/main/java/seedu/address/model/UserPrefs.java	3	90.63%
src/main/java/seedu/address/model/ModelManager.java	4	93.33%
src/main/java/seedu/address/model/util/DateTimeUtil.java	5	87.18%
src/main/java/seedu/address/logic/commands/AddHistCommand.java	6	87.14%
src/main/java/seedu/address/logic/parser/AddressBookParser.java	7	78.13%
src/main/java/seedu/address/logic/parser/ParserUtil.java	16	89.82%
src/main/java/seedu/address/logic/commands/EditHistCommand.java	32	37.78%
<!--	Total:	79		-->

Totals
Change from base Build 740:	7.6%
Covered Lines:	2966
Relevant Lines:	3592

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💛 - Coveralls