Username to UUID hash entry should be invalidated if UUID no more exists

[sentry-io]

Sentry Issue: CHRLY-D

Stacktrace (most recent call first):

  File "/home/travis/.gimme/versions/go1.14.linux.amd64/src/reflect/value.go", line 460, in call
  File "/home/travis/.gimme/versions/go1.14.linux.amd64/src/reflect/value.go", line 321, in Call
  File "/home/travis/gopath/src/github.com/elyby/chrly/vendor/github.com/asaskevich/EventBus/event_bus.go", line 158, in doPublish
  File "/home/travis/gopath/src/github.com/elyby/chrly/vendor/github.com/asaskevich/EventBus/event_bus.go", line 144, in Publish
  File "/home/travis/gopath/src/github.com/elyby/chrly/dispatcher/dispatcher.go", line 27, in Emit
  File "/home/travis/gopath/src/github.com/elyby/chrly/mojangtextures/mojang_textures.go", line 196, in getTextures
  File "/home/travis/gopath/src/github.com/elyby/chrly/mojangtextures/mojang_textures.go", line 157, in getResult
  File "/home/travis/gopath/src/github.com/elyby/chrly/mojangtextures/mojang_textures.go", line 132, in getResultAndBroadcast

textures: Unexpected Mojang response error: 200: Empty Response