Fix test failure

Now http_parser_parse_url returns nonzero if empty URI is given.

src/http2.cc

@@ -1581,6 +1581,10 @@ int construct_push_component(BlockAllocator &balloc, StringRef &scheme,
   int rv;
   StringRef rel, relq;
 
+  if (uri.size() == 0) {
+    return -1;
+  }
+
   http_parser_url u{};
 
   rv = http_parser_parse_url(uri.c_str(), uri.size(), 0, &u);

src/http2_test.cc

@@ -995,12 +995,8 @@ void test_http2_construct_push_component(void) {
 
   uri = StringRef{};
 
-  CU_ASSERT(0 == http2::construct_push_component(balloc, scheme, authority,
-                                                 path, base, uri));
-  CU_ASSERT("" == scheme);
-  CU_ASSERT("" == authority);
-  CU_ASSERT("/" == path);
-
+  CU_ASSERT(-1 == http2::construct_push_component(balloc, scheme, authority,
+                                                  path, base, uri));
   scheme = StringRef{};
   authority = StringRef{};
   path = StringRef{};