Safely check for out of date databases

When checking to re-import test databases, if the target database is
missing or otherwise unavailable, avoid the check and just continue.

This avoids a bug where a user would delete a test database and there
would be an error when trying to run a query.

extensions/ql-vscode/src/databases/local-databases/database-manager.ts

@@ -227,8 +227,16 @@ export class DatabaseManager extends DisposableObject {
       "codeql-database.yml",
     );
 
+    let originStat;
+    try {
+      originStat = await stat(originDbYml);
+    } catch (e) {
+      // if there is an error here, assume that the origin database
+      // is no longer available. Safely ignore and do not try to re-import.
+      return false;
+    }
+
     try {
-      const originStat = await stat(originDbYml);
       const importedStat = await stat(importedDbYml);
       return originStat.mtimeMs > importedStat.mtimeMs;
     } catch (e) {