fix: handle EmptyResult in stylelint to prevent _postcssResult from being empty

Author: liukonghe

.changeset/dry-pots-cry.md

@@ -0,0 +1,5 @@
+---
+'vite-plugin-checker': patch
+---
+
+handle EmptyResult in stylelint to prevent _postcssResult from being empty

packages/vite-plugin-checker/src/logger.ts

@@ -421,10 +421,12 @@ export function normalizeStylelintDiagnostic(
           column: d.endColumn,
         },
       }
-
+      let cssSource = ''
+      if (diagnostic._postcssResult && 'css' in diagnostic._postcssResult) {
+        cssSource = diagnostic._postcssResult.css
+      }
       const codeFrame = createFrame({
-        // @ts-ignore
-        source: diagnostic._postcssResult.css ?? '',
+        source: cssSource,
         location: loc,
       })