fix NPE at compareNumber() when filtering index query

[javeme]

fix #611

Change-Id: I20d841a85f82fb120244834538dc89c0d8f5ce27

[codecov]

Codecov Report

Merging #629 into master will increase coverage by 0.08%.
The diff coverage is 37.93%.

@@             Coverage Diff              @@
##             master     #629      +/-   ##
============================================
+ Coverage     72.36%   72.45%   +0.08%     
- Complexity     3740     3741       +1     
============================================
  Files           218      218              
  Lines         17296    17313      +17     
  Branches       2437     2455      +18     
============================================
+ Hits          12517    12544      +27     
+ Misses         3498     3483      -15     
- Partials       1281     1286       +5

Impacted Files	Coverage Δ	Complexity Δ
.../hugegraph/backend/serializer/TableSerializer.java	81.34% <ø> (ø)	52 <0> (ø)	⬇️
...c/main/java/com/baidu/hugegraph/util/DateUtil.java	56% <100%> (+1.83%)	6 <1> (ø)	⬇️
...m/baidu/hugegraph/backend/tx/GraphTransaction.java	82.65% <100%> (+0.05%)	210 <3> (ø)	⬇️
...a/com/baidu/hugegraph/backend/query/Condition.java	64.78% <11.11%> (-4.2%)	25 <0> (ø)
...du/hugegraph/backend/tx/GraphIndexTransaction.java	83.35% <66.66%> (+3.05%)	166 <0> (ø)	⬇️
.../java/com/baidu/hugegraph/structure/HugeIndex.java	69.73% <0%> (+2.63%)	23% <0%> (+1%)	⬆️

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[codecov]

Codecov Report

Merging #629 into master will decrease coverage by 20.34%.
The diff coverage is 45.94%.

@@              Coverage Diff              @@
##             master     #629       +/-   ##
=============================================
- Coverage     69.46%   49.11%   -20.35%     
+ Complexity     3629     2686      -943     
=============================================
  Files           218      218               
  Lines         17296    17328       +32     
  Branches       2437     2459       +22     
=============================================
- Hits          12014     8510     -3504     
- Misses         4050     7789     +3739     
+ Partials       1232     1029      -203

Impacted Files	Coverage Δ	Complexity Δ
...egraph/backend/store/cassandra/CassandraTable.java	81.32% <ø> (ø)	75 <0> (ø)	⬇️
...aidu/hugegraph/backend/store/mysql/MysqlTable.java	0% <ø> (-79.87%)	0 <0> (-74)
...ugegraph/backend/store/memory/InMemoryDBTable.java	20.83% <0%> (-60.42%)	9 <0> (-26)
...n/java/com/baidu/hugegraph/structure/HugeEdge.java	72.77% <0%> (-0.41%)	67 <0> (ø)
...src/main/java/com/baidu/hugegraph/HugeFactory.java	68% <100%> (ø)	6 <0> (ø)	⬇️
.../hugegraph/backend/serializer/TableSerializer.java	81.34% <100%> (ø)	52 <0> (ø)	⬇️
...du/hugegraph/traversal/optimize/TraversalUtil.java	67.38% <100%> (ø)	74 <0> (+1)	⬆️
...java/com/baidu/hugegraph/structure/HugeVertex.java	76.85% <100%> (-0.34%)	64 <0> (ø)
...c/main/java/com/baidu/hugegraph/util/DateUtil.java	56% <100%> (+1.83%)	6 <1> (ø)	⬇️
...ugegraph/backend/store/BackendProviderFactory.java	73.33% <100%> (+0.91%)	4 <2> (ø)	⬇️
... and 102 more

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