add empty references tests

test/built-ins/RegExp/named-groups/non-unicode-malformed.js

@@ -23,6 +23,7 @@ assert(/\k<a/.test("k<a"));
 assert(/\k/.test("k"));
 assert.throws(SyntaxError, () => eval("/(?<a>.)\\k/"));
 assert.throws(SyntaxError, () => eval("/(?<a>.)\\k<a/"));
+assert.throws(SyntaxError, () => eval("/(?<a>.)\\k<>/"));
 assert.throws(SyntaxError, () => eval("/(?<a>.)\\k<b>/"));
 assert.throws(SyntaxError, () => eval("/(?<a>a)\\k<ab>/"));
 assert.throws(SyntaxError, () => eval("/(?<ab>a)\\k<a>/"));

test/built-ins/RegExp/named-groups/unicode-malformed.js

@@ -16,9 +16,11 @@ assert.throws(SyntaxError, () => eval("/(?<a>a)(?<a>a)/u"), "Duplicate name");
 assert.throws(SyntaxError, () => eval("/(?<a>a)(?<b>b)(?<a>a)/u"), "Duplicate name");
 assert.throws(SyntaxError, () => eval("/\\k<a>/u"), "Invalid reference");
 assert.throws(SyntaxError, () => eval("/\\k<a/u"), "Unterminated reference");
+assert.throws(SyntaxError, () => eval("/\\k<>/u"), "Empty reference");
 assert.throws(SyntaxError, () => eval("/\\k/u"), "Lone \k");
 assert.throws(SyntaxError, () => eval("/(?<a>.)\\k/u"), "Lone \k");
 assert.throws(SyntaxError, () => eval("/(?<a>.)\\k<a/u"), "Unterminated reference");
+assert.throws(SyntaxError, () => eval("/(?<a>.)\\k<>/u"), "Empty reference");
 assert.throws(SyntaxError, () => eval("/(?<a>.)\\k<b>/u"), "Invalid reference");
 assert.throws(SyntaxError, () => eval("/(?<a>a)\\k<ab>/u"), "Invalid reference");
 assert.throws(SyntaxError, () => eval("/(?<ab>a)\\k<a>/u"), "Invalid reference");