fix: Travis: some layers needlessly re-run switch-client

Fixes #6466

Author: starpit

.travis.yml

@@ -47,7 +47,7 @@ install:
   - if [ -n "$NEEDS_MINIO" ]; then ./tools/travis/minio.sh & minio=$!; fi
   - npm ci
   - if [ -n "$NEEDS_IBMCLOUD" ]; then ./tools/travis/ibmcloud.sh && ./tools/travis/ibmcloud-plugin-build-install.sh; fi
-  - if [ "$CLIENT" != "default" ]; then ./bin/switch-client.sh ${CLIENT-default}; fi
+  - if [ -n "$CLIENT" ] && [ "$CLIENT" != "default" ]; then ./bin/switch-client.sh ${CLIENT-default}; fi
   - ./tools/codecov/instrument.sh
   - if [ "$MOCHA_RUN_TARGET" = "webpack" ]; then export KUI_USE_PROXY=true; if [ "$DEPLOY" = "cluster" ]; then npx kui-build-webpack && npx kui-build-docker-with-proxy && (kui-run-cproxy &); else npm run watch:webpack; fi; elif [ -z "$TEST_FROM_BUILD" ]; then npm run watch:electron; else npm run build:electron:$TRAVIS_OS_NAME:${TRAVIS_CPU_ARCH-amd64}; fi
   - if [ -n "$ow" ]; then wait $ow; fi