fix: handle empty YAML locale files gracefully

[kainstar]

Problem

When a locale file is empty, js-yaml's load() returns null instead of an object. This null value is then passed directly to either setProperty (when namespaceResolution is enabled) or used as resBundle[lang] (when it isn't). In both cases, a subsequent merge() call can silently discard previously loaded content for that locale — i.e. if a locale directory contains both a populated file and an empty file with the same namespace, the empty file's null result can overwrite the populated one.

Fix

Add a ?? {} fallback after loadAndParse() so that empty files are treated as empty objects, leaving all other locale content unaffected.

- const content = loadAndParse(langFile)
+ const content = loadAndParse(langFile) ?? {}