Merge #15917: wallet: Avoid logging no_such_file_or_directory error

70c1cf8c1c wallet: Avoid logging no_such_file_or_directory error (João Barbosa)

Pull request description:

  Avoid logging `IsBerkeleyBtree: No such file or directory ...`. The result of `IsBerkeleyBtree` is the same since `fs::file_size()` returns 0 for non existent files.

  Fix #15912.

ACKs for commit 70c1cf:
  practicalswift:
    utACK 70c1cf8c1c
  jonasschnelli:
    utACK 70c1cf8c1c
  Empact:
    utACK 70c1cf8c1c

Tree-SHA512: 964a64fff9a17b805a1570884cdb2beb82283498f790b0464e011791803ae7f37dba213320c76a920dd92b2b972a7640e6277ecf470400734149dc8f9f9f1d6d

src/wallet/walletutil.cpp

@@ -31,6 +31,8 @@ fs::path GetWalletDir()
 
 static bool IsBerkeleyBtree(const fs::path& path)
 {
+    if (!fs::exists(path)) return false;
+
     // A Berkeley DB Btree file has at least 4K.
     // This check also prevents opening lock files.
     boost::system::error_code ec;