travis-ci: don't try to decrypt updates key for PRs

.travis.yml

@@ -43,8 +43,7 @@ deploy:
 
 before_install:
   - git fetch --unshallow
-  - openssl aes-256-cbc -K $encrypted_a1949b55824a_key -iv $encrypted_a1949b55824a_iv 
-    -in private/www-updater.key.enc -out private/www-updater.key -d
+  - "[ $TRAVIS_PULL_REQUEST == 'false' ] && openssl aes-256-cbc -K $encrypted_a1949b55824a_key -iv $encrypted_a1949b55824a_iv -in private/www-updater.key.enc -out private/www-updater.key -d || :"
 
 # before_install:
   # required libs for android build tools