Avoid empty \"If-Modified-Since\" header in validation request

Author: mpdude

HttpCache/HttpCache.php

@@ -352,7 +352,9 @@ protected function validate(Request $request, Response $entry, $catch = false)
  }
 
  // add our cached last-modified validator
- $subRequest->headers->set('if_modified_since', $entry->headers->get('Last-Modified'));
+ if ($entry->headers->has('Last-Modified')) {
+ $subRequest->headers->set('if_modified_since', $entry->headers->get('Last-Modified'));
+ }
 
  // Add our cached etag validator to the environment.
  // We keep the etags from the client to handle the case when the client

Tests/HttpCache/HttpCacheTest.php

@@ -859,6 +859,7 @@ public function testValidatesCachedResponsesUseSameHttpMethod()
  public function testValidatesCachedResponsesWithETagAndNoFreshnessInformation()
  {
  $this->setNextResponse(200, [], 'Hello World', function ($request, $response) {
+ $this->assertFalse($request->headers->has('If-Modified-Since'));
  $response->headers->set('Cache-Control', 'public');
  $response->headers->set('ETag', '"12345"');
  if ($response->getETag() == $request->headers->get('IF_NONE_MATCH')) {