Fix exception when fetching empty collections

lib/shared/wp-request.js

@@ -220,7 +220,14 @@ function mergeUrl( endpoint, linkPath ) {
  *                   pagination metadata
  */
 function paginateResponse( result, endpoint ) {
-	if ( ! result.headers || ! result.headers['x-wp-totalpages'] ) {
+	if ( ! result.headers || ! result.headers.link ) {
+		// No headers: return as-is
+		return result;
+	}
+
+	var totalPages = result.headers['x-wp-totalpages'];
+
+	if ( ! totalPages || totalPages === '0' || totalPages === '1' ) {
 		// No paging: return as-is
 		return result;
 	}
@@ -231,7 +238,7 @@ function paginateResponse( result, endpoint ) {
 	// Store pagination data from response headers on the response collection
 	result.body._paging = {
 		total: result.headers['x-wp-total'],
-		totalPages: result.headers['x-wp-totalpages'],
+		totalPages: totalPages,
 		links: links
 	};
 

tests/lib/shared/wp-request.js

@@ -402,12 +402,36 @@ describe( 'WPRequest', function() {
 				});
 			});
 
-			it( 'passes data through unchanged if no pagination headers are present', function() {
+			it( 'passes data through unchanged if no headers are present', function() {
 				mockAgent._response = {
-					headers: {},
 					body: 'some object'
 				};
-				wpRequest.then(function(parsedResult) {
+				return wpRequest.then(function(parsedResult) {
+					expect( parsedResult ).to.equal( 'some object' );
+					expect( parsedResult ).not.to.have.property( '_paging' );
+				});
+			});
+
+			it( 'passes data through unchanged if header has no link property', function() {
+				mockAgent._response = {
+					headers: {
+						'x-wp-totalpages': '0',
+						'x-wp-total': '0'
+					},
+					body: 'some object'
+				};
+				return wpRequest.then(function(parsedResult) {
+					expect( parsedResult ).to.equal( 'some object' );
+					expect( parsedResult ).not.to.have.property( '_paging' );
+				});
+			});
+
+			it( 'passes data through unchanged if pagination header is unset or empty', function() {
+				mockAgent._response = {
+					headers: { link: '' },
+					body: 'some object'
+				};
+				return wpRequest.then(function(parsedResult) {
 					expect( parsedResult ).to.equal( 'some object' );
 					expect( parsedResult ).not.to.have.property( '_paging' );
 				});