136 error on non existent word

[kod-kristoff]

• refactor: return None on non-existing
• fix: handle response errors

Bug Fix Title

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Expected Behavior

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Fixes #136

[codecov]

Codecov Report

Attention: Patch coverage is 93.54839% with 2 lines in your changes missing coverage. Please review.

Project coverage is 52.2%. Comparing base (05935b1) to head (42ee6d6).

Additional details and impacted files

Files	Coverage Δ
src/sblex/application/services/lookup.py	52.5% <100.0%> (+1.2%)	⬆️
src/sblex/fm_server/api/morph.py	100.0% <100.0%> (ø)
src/sblex/infrastructure/queries/http_morpology.py	100.0% <100.0%> (+14.2%)	⬆️
src/sblex/saldo_ws/routes/fullform_lex.py	100.0% <100.0%> (ø)
src/sblex/trie/trie.py	98.6% <100.0%> (ø)
src/sblex/fm/morphology.py	78.1% <75.0%> (+5.3%)	⬆️