fix index existence check

[czpmango]

Fixes #3312 and #2842

[codecov-commenter]

Codecov Report

Merging #3315 (f0ea53d) into master (80e827f) will increase coverage by 0.00%.
The diff coverage is 87.14%.

@@           Coverage Diff           @@
##           master    #3315   +/-   ##
=======================================
  Coverage   85.24%   85.24%           
=======================================
  Files        1289     1289           
  Lines      120035   120100   +65     
=======================================
+ Hits       102322   102378   +56     
- Misses      17713    17722    +9     

Impacted Files	Coverage Δ
src/graph/executor/admin/ShowTSClientsExecutor.cpp	0.00% <0.00%> (ø)
src/graph/optimizer/OptGroup.h	100.00% <ø> (ø)
src/graph/optimizer/Optimizer.h	100.00% <ø> (ø)
src/graph/optimizer/OptimizerUtils.cpp	94.00% <ø> (ø)
...h/optimizer/rule/GeoPredicateIndexScanBaseRule.cpp	96.20% <ø> (ø)
src/graph/optimizer/rule/IndexScanRule.cpp	71.98% <ø> (ø)
...timizer/rule/OptimizeEdgeIndexScanByFilterRule.cpp	90.54% <ø> (ø)
...ptimizer/rule/OptimizeTagIndexScanByFilterRule.cpp	90.27% <ø> (ø)
...graph/optimizer/rule/PushFilterDownGetNbrsRule.cpp	75.51% <ø> (ø)
...imizer/rule/PushLimitDownEdgeIndexFullScanRule.cpp	89.65% <ø> (ø)
... and 58 more

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[yixinglu]

LGTM