Add safeguard against unexpected response header capitalization

May address #332

Author: kadamwhite

lib/http-transport.js

@@ -120,14 +120,24 @@ function extractResponseBody( response ) {
 function createPaginationObject( result, options, httpTransport ) {
 	let _paging = null;
 
-	if ( ! result.headers || ! result.headers[ 'x-wp-totalpages' ] ) {
+	if ( ! result.headers ) {
 		// No headers: return as-is
 		return _paging;
 	}
 
+	// Guard against capitalization inconsistencies in returned headers
+	Object.keys( result.headers ).forEach( ( header ) => {
+		result.headers[ header.toLowerCase() ] = result.headers[ header ];
+	} );
+
+	if ( ! result.headers[ 'x-wp-totalpages' ] ) {
+		// No paging: return as-is
+		return _paging;
+	}
+
 	const totalPages = +result.headers[ 'x-wp-totalpages' ];
 
-	if ( ! totalPages || totalPages === '0' ) {
+	if ( ! totalPages || totalPages === 0 ) {
 		// No paging: return as-is
 		return _paging;
 	}