The change is in the release notes the 0.4.6 release:
- Compile-time checks for Particle.variable() #619
The check is there because the code you wrote is in fact wrong and won’t work the way you think it might. So I’m sorry for your frustration but this is meant to help you.
If you don’t want your devices automatically updated to the latest version of firmware, you can select a version other than “latest” for your device in the “devices” drawer of the Web IDE.