[ngrams] fix sql query to return arrays without NULL

This was the case before
4 jobs for 518-dev-ngrams-table-sql-optimization in 58 minutes and 57 seconds (queued for 5 seconds)
latest
Status Job ID Name Coverage
  Cabal
passed #19621
cabal

00:28:34

 
  Stack
passed #19622
stack

00:03:15

 
  Bench
manual #19623
allowed to fail manual
bench
 
  Test
failed #19624
test

00:27:07

 
Name Stage Failure
failed
test Test
/builds/gargantext/haskell-gargantext/dist-newstyle/build/x86_64-linux/ghc-9.6.6/gargantext-0.0.7.5.3/t/garg-test/opt/test/gargantext-0.0.7.5.3-garg-test.log
0 of 1 test suites (0 of 1 test cases) passed.
Error: [Cabal-7125]
Tests failed for gargantext-0.0.7.5.3-inplace-garg-test.
CallStack (from HasCallStack):
dieWithException, called at src/Distribution/Client/ProjectOrchestration.hs:1232:21 in cabal-install-3.12.1.0-4VzemddeTcy9Sd7ImiySSq:Distribution.Client.ProjectOrchestration

Cleaning up project directory and file based variables
ERROR: Job failed: exit code 1