Fix non-release docker builds (#357)

Merge branch 'master' into bugfix/local-docker-builds

Fix non-release docker builds

Co-authored-by: konrad <konrad@kola-entertainments.de>
Co-authored-by: branchmispredictor <msm595dev@gmail.com>
Reviewed-on: vikunja/frontend#357
Reviewed-by: konrad <konrad@kola-entertainments.de>
Co-Authored-By: branchmispredictor <branchmispredictor@noreply.mowie.cc>
Co-Committed-By: branchmispredictor <branchmispredictor@noreply.mowie.cc>

Dockerfile

@@ -10,7 +10,7 @@ ENV YARN_CACHE_FOLDER .cache/yarn/
 COPY .  ./
 
 RUN \
-  if [ $USE_RELEASE ]; then \
+  if [ $USE_RELEASE = true ]; then \
     rm -rf dist/ && \
     wget https://dl.vikunja.io/frontend/vikunja-frontend-$RELEASE_VERSION.zip -O frontend-release.zip && \
     unzip frontend-release.zip -d dist/ && \
@@ -42,4 +42,4 @@ ENV PGID 1000
 
 LABEL maintainer="maintainers@vikunja.io"
 
-CMD "/run.sh"
+CMD "/run.sh"