Add failure tests for FPDFPage_Delete().

Change-Id: I2352bbcfb9e10ea6bfc855b2e0ccb392902c3844
Reviewed-on: https://pdfium-review.googlesource.com/c/50712
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>

fpdfsdk/fpdf_doc_embeddertest.cpp

diff --git a/fpdfsdk/fpdf_doc_embeddertest.cpp b/fpdfsdk/fpdf_doc_embeddertest.cpp
index 33f119a..13f27d9 100644
--- a/fpdfsdk/fpdf_doc_embeddertest.cpp
+++ b/fpdfsdk/fpdf_doc_embeddertest.cpp
@@ -429,6 +429,15 @@
 TEST_F(FPDFDocEmbedderTest, DeletePage) {
   EXPECT_TRUE(OpenDocument("hello_world.pdf"));
   EXPECT_EQ(1, FPDF_GetPageCount(document()));
+
+  FPDFPage_Delete(nullptr, 0);
+  EXPECT_EQ(1, FPDF_GetPageCount(document()));
+
+  FPDFPage_Delete(document(), -1);
+  EXPECT_EQ(1, FPDF_GetPageCount(document()));
+  FPDFPage_Delete(document(), 1);
+  EXPECT_EQ(1, FPDF_GetPageCount(document()));
+
   FPDFPage_Delete(document(), 0);
   EXPECT_EQ(0, FPDF_GetPageCount(document()));
 }