Fix botched negation in cpdf_imageobject.cpp

Regressed at https://pdfium.googlesource.com/pdfium/+/7d4f6a89d7e2c5d13b7d630d6348950044a5465e

TBR=thestig@chromium.org
Change-Id: I25b8d6b4847090af18c9f36e4cea07a1eeb2a99a
Reviewed-on: https://pdfium-review.googlesource.com/4500
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>
diff --git a/core/fpdfapi/page/cpdf_imageobject.cpp b/core/fpdfapi/page/cpdf_imageobject.cpp
index 1c2cc6b..8732c00 100644
--- a/core/fpdfapi/page/cpdf_imageobject.cpp
+++ b/core/fpdfapi/page/cpdf_imageobject.cpp
@@ -61,7 +61,7 @@
     return;
 
   CPDF_DocPageData* pPageData = pDocument->GetPageData();
-  if (pPageData)
+  if (!pPageData)
     return;
 
   CPDF_Stream* pStream = m_pImage->GetStream();