Bug 1763679 - Null-check in PrintTargetPDF, rather than relying on the caller to do so. r=hiro

Differential Revision: https://phabricator.services.mozilla.com/D143245

gfx/thebes/PrintTargetPDF.cpp

@@ -49,6 +49,10 @@ PrintTargetPDF::~PrintTargetPDF() {
 /* static */
 already_AddRefed<PrintTargetPDF> PrintTargetPDF::CreateOrNull(
     nsIOutputStream* aStream, const IntSize& aSizeInPoints) {
+  if (NS_WARN_IF(!aStream)) {
+    return nullptr;
+  }
+
   cairo_surface_t* surface = cairo_pdf_surface_create_for_stream(
       write_func, (void*)aStream, aSizeInPoints.width, aSizeInPoints.height);
   if (cairo_surface_status(surface)) {

widget/gtk/nsDeviceContextSpecG.cpp

@@ -110,10 +110,6 @@ already_AddRefed<PrintTarget> nsDeviceContextSpecGTK::MakePrintTarget() {
     return stream;
   }();
 
-  if (!stream) {
-    return nullptr;
-  }
-
   return PrintTargetPDF::CreateOrNull(stream, IntSize::Ceil(width, height));
 }