functions.php has $haystack and errors

Not sure if it was an update or what changed this. It worked one day, the next it loads to this error page. I was told by hosting support to rebuild core files but I have never done that before and sounds daunting. If you visit the site you see these errors (copy and pasted here):

Deprecated: strpos(): Passing null to parameter #1 ($haystack) of type string is deprecated in /home/mslandscape/public_html/wp-includes/functions.php on line 7288

Deprecated: str_replace(): Passing null to parameter #3 ($subject) of type array|string is deprecated in?/home/mslandscape/public_html/wp-includes/functions.php?on line?2187

I have no clue but here’s the sections of code each refers to, respectively:

/**

• Tests if a given path is a stream URL
  *
• @since 3.5.0
  *
• @param string $path The resource path or URL.
• @return bool True if the path is a stream URL.
  */
  function wp_is_stream( $path ) {
  $scheme_separator = strpos( $path, ‘://’ ); if ( false === $scheme_separator ) {
  // $path isn’t a stream.
  return false;
  } $stream = substr( $path, 0, $scheme_separator ); return in_array( $stream, stream_get_wrappers(), true );
  }

line 7288 is bolded ($scheme_separator = strpos( $path, ‘://’ );)

/**

• Normalizes a filesystem path.
  *
• On windows systems, replaces backslashes with forward slashes
• and forces upper-case drive letters.
• Allows for two leading slashes for Windows network shares, but
• ensures that all other duplicate slashes are reduced to a single.
  *
• @since 3.9.0
• @since 4.4.0 Ensures upper-case drive letters on Windows systems.
• @since 4.5.0 Allows for Windows network shares.
• @since 4.9.7 Allows for PHP file wrappers.
  *
• @param string $path Path to normalize.
• @return string Normalized path.
  */
  function wp_normalize_path( $path ) {
  $wrapper = ”; if ( wp_is_stream( $path ) ) {
  list( $wrapper, $path ) = explode( ‘://’, $path, 2 ); $wrapper .= '://'; } // Standardize all paths to use ‘/’.
  $path = str_replace( ‘\’, ‘/’, $path ); // Replace multiple slashes down to a singular, allowing for network shares having two slashes.
  $path = preg_replace( ‘|(?<=.)/+|’, ‘/’, $path ); // Windows paths should uppercase the drive letter.
  if ( ‘:’ === substr( $path, 1, 1 ) ) {
  $path = ucfirst( $path );
  } return $wrapper . $path;
  }

2187 is bolded. ($path = str_replace( ‘\’, ‘/’, $path );)

The page I need help with: [log in to see the link]