fix: treat missing complementation file as non-fatal

Agent-Logs-Url: https://github.com/securefolderfs-community/SecureFolderFS/sessions/97747175-69cf-4f84-9b88-ba52b9ef01f2

Co-authored-by: d2dyno1 <53011783+d2dyno1@users.noreply.github.com>

Author: Copilot

src/Core/SecureFolderFS.Core/VaultAccess/VaultReader.cs

@@ -55,8 +55,15 @@ public async Task<V4VaultConfigurationDataModel> ReadV4ConfigurationAsync(Cancel
 
         public async Task<VaultSharesDataModel?> ReadComplementationAsync(CancellationToken cancellationToken)
         {
-            if (await _vaultFolder.GetFirstByNameAsync(Constants.Vault.Names.VAULT_COMPLEMENTATION_FILENAME, cancellationToken) is not IFile complementFile)
+            IFile complementFile;
+            try
+            {
+                complementFile = await _vaultFolder.GetFileByNameAsync(Constants.Vault.Names.VAULT_COMPLEMENTATION_FILENAME, cancellationToken);
+            }
+            catch (FileNotFoundException)
+            {
                 return null;
+            }
 
             return await ReadDataAsync<VaultSharesDataModel?>(complementFile, _serializer, cancellationToken);
         }