fix(frontend): add guard against null model

[afsuyadi]

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Changes

Contributes to #7511

1. Error happens when CompareIdentities component is trying to access variable environments
2. That variable is accessed by calling ProjectStore component, and then executing method getEnvironmentIdFromKey()
3. By observing method getEnvironmentIdFromKey() inside file project-store.js, it can be deduced that the error happens when object store.model is still null
4. To prevent this error when component CompareIdentities is still rendered, I add guard to ensure store.model is accessed only when it has value.

How did you test this code?

1. I try to reproduce the issue in my local environment, by observing the console before and after the fix has been applied.
2. However, it seems that the error is quite difficult to be reproduced, as this error seems to happen in Sentry environment. CMIIW.

Before fix:
Screencast from 13-06-26 07:26:56.webm

After fix:
Screencast from 13-06-26 07:30:07.webm

[vercel]

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