Issue 43090. Catch parser exceptions in available declarations.

Bug: #43090
Change-Id: Ia4cd891842bfdc7ac0b6a7755a916032bccfa202
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/181340
Reviewed-by: Samuel Rawlins <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>

Author: scheglov

pkg/analyzer/lib/src/services/available_declarations.dart

@@ -1920,11 +1920,19 @@ class _File {
   }
 
   static CompilationUnit _parse(FeatureSet featureSet, String content) {
-    return parseString(
-      content: content,
-      featureSet: featureSet,
-      throwIfDiagnostics: false,
-    ).unit;
+    try {
+      return parseString(
+        content: content,
+        featureSet: featureSet,
+        throwIfDiagnostics: false,
+      ).unit;
+    } catch (e) {
+      return parseString(
+        content: '',
+        featureSet: featureSet,
+        throwIfDiagnostics: false,
+      ).unit;
+    }
   }
 
   static String _readContent(File resource) {