fix(cli): guard against empty translations in PO loader push (#2000)

When a .po file section contains only obsolete entries or no
translations, Object.keys() on undefined csEntries throws a TypeError.
Add guards to skip sections with empty translations in the
currentSections.find() callback, matching the existing pattern used
in the outer map.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: cherkanovart

.changeset/fix-po-loader-crash.md

@@ -0,0 +1,5 @@
+---
+"lingo.dev": patch
+---
+
+Fix crash in PO loader when current section has no translations

packages/cli/src/cli/loaders/po/index.ts

@@ -67,8 +67,14 @@ export function createPoDataLoader(
           // If the section is empty, try to find it in the current sections
           const currentSection = currentSections.find((cs) => {
             const csPo = gettextParser.po.parse(cs);
+            if (Object.keys(csPo.translations).length === 0) {
+              return false;
+            }
             const csContextKey = _.keys(csPo.translations)[0];
             const csEntries = csPo.translations[csContextKey];
+            if (!csEntries) {
+              return false;
+            }
             const csMsgid = Object.keys(csEntries).find(
               (key) => csEntries[key].msgid,
             );