fix: move None guard above yaml.dump to avoid writing null to debug file

## What

Moved the `if dependabot_file is None` check above the `yaml.dump()` call in `main()` so that None results skip immediately without writing `null` to `dependabot-output.yaml`.

## Why

The previous ordering called `yaml.dump(None, yaml_file)` before checking for None, writing a `null` YAML literal to the debug artifact. This was a pre-existing issue for the "no package managers" path, but the YAML error handling change made it newly reachable via the error path.

## Notes

- The YAML object and stream setup also moved below the guard since they're only needed when dependabot_file is not None.

Signed-off-by: jmeridth <jmeridth@gmail.com>

Author: jmeridth

evergreen.py

@@ -178,6 +178,10 @@ def main():  # pragma: no cover
             cooldown,
         )
 
+        if dependabot_file is None:
+            print("\tNo (new) compatible package manager found")
+            continue
+
         yaml = ruamel.yaml.YAML()
         stream = io.StringIO()
         yaml.indent(mapping=2, sequence=4, offset=2)
@@ -186,10 +190,6 @@ def main():  # pragma: no cover
         with open("dependabot-output.yaml", "w", encoding="utf-8") as yaml_file:
             yaml.dump(dependabot_file, yaml_file)
 
-        if dependabot_file is None:
-            print("\tNo (new) compatible package manager found")
-            continue
-
         dependabot_file = yaml.dump(dependabot_file, stream)
         dependabot_file = stream.getvalue()