Fix empty .env file handling when isOptional=true

[Copilot]

When a .env file exists but is empty, DotEnv().load() with isOptional=true was throwing an EmptyEnvFileError, which is inconsistent with how missing files are handled (they don't throw when isOptional=true).

Problem

The load() method only caught FileNotFoundError but not EmptyEnvFileError. When an empty .env file exists:

1. _getEntriesFromFile() successfully loads the file but finds it empty
2. It throws EmptyEnvFileError
3. The load() method doesn't catch this exception, so it propagates up even when isOptional=true

This creates inconsistent behavior where:

• Missing file + isOptional=true → ✅ Works (no exception)
• Empty file + isOptional=true → ❌ Throws EmptyEnvFileError

Solution

Added a catch block for EmptyEnvFileError that mirrors the exact same logic as the existing FileNotFoundError handler:

} on EmptyEnvFileError {
  if (isOptional) {
    linesFromFile = [];
  } else {
    rethrow;
  }
}

Now both missing and empty files behave consistently when isOptional=true - they both set linesFromFile = [] and continue processing normally.

Testing

Added comprehensive tests in test/empty_env_test.dart covering all scenarios:

• Empty file with isOptional=true (should not throw)
• Empty file with isOptional=false (should throw EmptyEnvFileError)
• Missing file with isOptional=true (should not throw - existing behavior)
• Missing file with isOptional=false (should throw FileNotFoundError - existing behavior)

Fixes #125.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• dl-ssl.google.com
  • Triggering command: wget -qO- REDACTED (dns block)
  • Triggering command: curl -fsSL REDACTED (dns block)
• esm.ubuntu.com
  • Triggering command: /usr/lib/apt/methods/https (dns block)
• https://storage.googleapis.com/flutter_infra_release/releases/stable/linux/flutter_linux_3.24.5-stable.tar.xz
  • Triggering command: wget -q REDACTED (http block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

---

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[Copilot]

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[java-james]

First time using code pilot to open PRs from issues :)

LGTM