fix exception of vertex-drop with index

[simon824]

closed #2062

According to @javeme 's solution (#2062 (comment)), the id will be filtered during querying vertices and properties will still be null(refer to the screenshot below).

And it works if force loading properties (forceLoad) before vertex being added to removedVertices in GraphTransaction.removeVertex().

[codecov]

Codecov Report

Merging #2181 (a99691d) into master (6997a87) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             master    #2181    +/-   ##
==========================================
  Coverage     65.08%   65.08%            
- Complexity      676      977   +301     
==========================================
  Files           497      497            
  Lines         40564    40566     +2     
  Branches       5662     5663     +1     
==========================================
+ Hits          26400    26402     +2     
- Misses        11549    11551     +2     
+ Partials       2615     2613     -2     

Impacted Files	Coverage Δ
.../apache/hugegraph/backend/tx/GraphTransaction.java	79.95% <100.00%> (+0.04%)	⬆️

... and 2 files with indirect coverage changes

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[imbajin]

thanks for the context