issue #128 crashes on {} in start of list item

tests with shift -1 was rolling around to end of array
when matching first child token

index.js

@@ -57,6 +57,12 @@ function test(tokens, i, t) {
   let ii = t.shift !== undefined
     ? i + t.shift
     : t.position;
+
+  if (t.shift !== undefined && ii < 0) {
+    // we should never shift to negative indexes (rolling around to back of array)
+    return res;
+  }
+
   let token = get(tokens, ii);  // supports negative ii
 
 

test.js

@@ -390,11 +390,17 @@ function describeTestsWithOptions(options, postText) {
       assert.equal(md.render(replaceDelimiters(src, options)), expected);
     });
 
-    it(replaceDelimiters('should support multiple classes for <hr>', options), () => {
+    it('should support multiple classes for <hr>', () => {
       src = '--- {.a .b}';
       expected = '<hr class="a b">\n';
       assert.equal(md.render(replaceDelimiters(src, options)), expected);
     });
+
+    it(replaceDelimiters('should not crash on {#ids} in front of list items', options), () => {
+      src = '- {#ids} [link](./link)';
+      expected = replaceDelimiters('<ul>\n<li>{#ids} <a href="./link">link</a></li>\n</ul>\n', options);
+      assert.equal(md.render(replaceDelimiters(src, options)), expected);
+    });
   });
 }