message: Fix error modal rendering
  Due to z-index, the modal was shown partially below the search bar in
  GameSelectionScreen.
diff: <router-view @error="showError" v-if="visible"/>
  - <div id='errorModal' :class="['modal', {'is-active':(errorMessage !== '')}]">
  + <div id='errorModal' :class="['modal', 'z-top', {'is-active':(errorMessage !== '')}]">
  <div class="modal-background" @click="closeErrorModal()"></div>
  <div class='modal-content'>
  <div class='notification is-danger'>
  