fix: handle empty publicStripeKey to prevent frontend crash (#5640) Additional changes

[iroussos25]

The Problem
Self-hosted instances were experiencing hard process exits during both the frontend hydration and backend initialization phases. This was caused by the unsafe use of non-null assertions (!) and the Stripe SDK attempting to initialize with empty strings or undefined values when environment variables were missing.

The Fix
I have implemented a defense-in-depth approach to ensure Nango remains stable even if Stripe credentials are not provided.

Key Changes:

Backend (Runtime Guard): Replaced unsafe non-null assertions in the Stripe service. The backend now performs a runtime check for STRIPE_SECRET_KEY before instantiation, preventing unhandled exceptions that lead to container crash-loops.

Frontend (SDK Guard): Updated the Webapp utility to conditionally load the Stripe SDK only when a valid publishable key is present. If missing, the promise resolves to null gracefully.

Environment Sanitization: Modified getEnvJs and the WindowEnv interface to sanitize empty environment strings to undefined, providing a predictable data flow for configuration.

UI Resilience: Added a defensive check in the billing upgrade flow to handle "Stripe Unavailable" states, ensuring the user is met with a handled UI state rather than a blank screen/crash.

Scope Note
This PR is strictly focused on environment handling and Stripe stability. It does not include unrelated workspace configuration changes.

Closes #5640

P.S. I’ve recently applied for the Software Engineering role (Giannis Roussos). While setting up my local environment and diving into the docs, I noticed this friction point for self-hosted users and figured a PR was the best way to introduce my engineering style to the team.

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This PR adds guards around Stripe initialization and usage to prevent crashes when Stripe environment variables are missing in self-hosted deployments. It replaces a non-null assertion with a runtime check on the backend, conditionally loads the Stripe SDK on the frontend, and updates the environment payload typing to allow undefined Stripe keys.

It also adds a UI-level fallback in the billing upgrade flow to show an error toast when Stripe is unavailable instead of proceeding with a null Stripe instance.

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This summary was automatically generated by @propel-code-bot

[propel-code-bot]

Review found no issues; changes appear appropriate and stable.

Status: No Issues Found | Risk: Low

Review Details

📁 5 files reviewed | 💬 0 comments

Instruction Files

└── .claude/
    ├── agents/
    │   └── nango-docs-migrator.md
    └── skills/
        ├── agent-builder-skill/
        │   ├── EXAMPLES.md
        │   └── SKILL.md
        ├── creating-integration-docs/
        │   └── SKILL.md
        └── creating-skills-skill/
            └── SKILL.md