fix(currencyConversion): no more crash when currency is unknown

* Updated utils functions for currency conversion and getting symbol
* Updated its used in the app

Fixes #76
Status Job ID Name Coverage
  Check
passed #481917
docker
check_back

00:00:22

passed #481918
docker
check_front

00:01:15

 
  Test
passed #481919
docker
test_back

00:00:44

87.0%
passed #481920
docker
test_frontend

00:01:01

 
  Lint
passed #481922
docker
eslint

00:01:14

passed #481921
docker
flake8

00:00:13

 
  Svg Gen Docu
passed #481923
docker
generate_UML_svg

00:00:15

 
  Documentation
passed #481924
docker
pages

00:00:12

 
  Deploy
passed pages:deploy

00:00:00