Fix small date deserialize bug

[Linary]

Change-Id: Ie9c48f2b672a3e45fc9394fe940369ff6953eee9

[Linary]

1970 -> -288000(Integer) -> PropertyKey.valueToDate() will return null

[codecov]

Codecov Report

Merging #1152 into master will decrease coverage by 0.45%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master    #1152      +/-   ##
============================================
- Coverage     65.85%   65.40%   -0.46%     
+ Complexity     5654     5631      -23     
============================================
  Files           355      355              
  Lines         28848    28850       +2     
  Branches       4053     4054       +1     
============================================
- Hits          18998    18869     -129     
- Misses         7965     8094     +129     
- Partials       1885     1887       +2     

Impacted Files	Coverage Δ	Complexity Δ
...java/com/baidu/hugegraph/type/define/DataType.java	86.40% <100.00%> (+0.26%)	53.00 <0.00> (+1.00)
...egraph/backend/store/mysql/MysqlStoreProvider.java	33.33% <0.00%> (-66.67%)	2.00% <0.00%> (-4.00%)
...aidu/hugegraph/backend/store/mysql/MysqlStore.java	63.95% <0.00%> (-17.77%)	44.00% <0.00%> (-1.00%)
...idu/hugegraph/backend/store/mysql/MysqlTables.java	76.34% <0.00%> (-13.27%)	1.00% <0.00%> (ø%)
...u/hugegraph/backend/store/mysql/MysqlSessions.java	57.53% <0.00%> (-10.96%)	18.00% <0.00%> (-9.00%)
...aidu/hugegraph/backend/store/mysql/MysqlTable.java	75.75% <0.00%> (-5.79%)	87.00% <0.00%> (-9.00%)
...baidu/hugegraph/backend/store/mysql/MysqlUtil.java	93.22% <0.00%> (-3.39%)	23.00% <0.00%> (ø%)
...va/com/baidu/hugegraph/task/ServerInfoManager.java	71.59% <0.00%> (-2.85%)	51.00% <0.00%> (-1.00%)
...ain/java/com/baidu/hugegraph/task/TaskManager.java	72.54% <0.00%> (-1.31%)	28.00% <0.00%> (ø%)
...a/com/baidu/hugegraph/backend/query/Condition.java	77.65% <0.00%> (-0.37%)	32.00% <0.00%> (ø%)

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