message: wallet: fix buffer over-read in SQLite file magic check
  If there is no terminating zero within the 16 magic bytes, the buffer would be
  over-read in the std::string constructor. Fixed by using the "from buffer"
  variant of the ctor (that also takes a size) rather than the "from c-string"
  variant.
diff: @@ -619,8 +619,8 @@ bool IsSQLiteFile(const fs::path& path)
  file.close();
  // Check the magic, see https://sqlite.org/fileformat2.html
  - std::string magic_str(magic);
  - if (magic_str != std::string("SQLite format 3")) {
  + std::string magic_str(magic, 16);
  + if (magic_str != std::string("SQLite format 3", 16)) {
  return false;
  }
  