Fix a memory leak in FPDFPageFuncEmbeddertest.

core/src/fpdfapi/fpdf_render/fpdf_render_pattern_embeddertest.cpp

 // Copyright 2015 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "testing/embedder_test.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 class FPDFRenderPatternEmbeddertest : public EmbedderTest {};
 
 TEST_F(FPDFRenderPatternEmbeddertest, LoadError_547706) {
   // Test shading where object is a dictionary instead of a stream.
   EXPECT_TRUE(OpenDocument("bug_547706.pdf"));
   FPDF_PAGE page = LoadPage(0);
-  RenderPage(page);
+  FPDF_BITMAP bitmap = RenderPage(page);
+  FPDFBitmap_Destroy(bitmap);
   UnloadPage(page);
 }