winhttp: Fix a test failure on Windows 8 and conform to the more recent behavior.

dlls/winhttp/session.c

@@ -1365,7 +1365,11 @@ BOOL WINAPI WinHttpDetectAutoProxyConfigUrl( DWORD flags, LPWSTR *url )
     FIXME("getaddrinfo not found at build time\n");
 #endif
     }
-    if (!ret) set_last_error( ERROR_WINHTTP_AUTODETECTION_FAILED );
+    if (!ret)
+    {
+        set_last_error( ERROR_WINHTTP_AUTODETECTION_FAILED );
+        *url = NULL;
+    }
     return ret;
 }
 

dlls/winhttp/tests/winhttp.c

@@ -2759,7 +2759,7 @@ if (0) /* crashes on some win2k systems */
     if (!ret)
     {
         ok( error == ERROR_WINHTTP_AUTODETECTION_FAILED, "got %u\n", error );
-        ok( url == (WCHAR *)0xdeadbeef, "got %p\n", url );
+        ok( !url || broken(url == (WCHAR *)0xdeadbeef), "got %p\n", url );
     }
     else
     {
@@ -2774,7 +2774,7 @@ if (0) /* crashes on some win2k systems */
     if (!ret)
     {
         ok( error == ERROR_WINHTTP_AUTODETECTION_FAILED, "got %u\n", error );
-        ok( url == (WCHAR *)0xdeadbeef, "got %p\n", url );
+        ok( !url || broken(url == (WCHAR *)0xdeadbeef), "got %p\n", url );
     }
     else
     {