restore intersect methods to use old-style empty-checks on their inputs

Bug introduced when we made isEmpty check for int32_t width/height

Bug:800804
Change-Id: I59799c88fb02f176c1545dd0edae050b510df079
Reviewed-on: https://skia-review.googlesource.com/93302
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Mike Reed <reed@google.com>
diff --git a/gn/gm.gni b/gn/gm.gni
index cdbe829..25c80bf 100644
--- a/gn/gm.gni
+++ b/gn/gm.gni
@@ -162,6 +162,7 @@
   "$_gm/hardstop_gradients.cpp",
   "$_gm/highcontrastfilter.cpp",
   "$_gm/hittestpath.cpp",
+  "$_gm/hugepath.cpp",
   "$_gm/hsl.cpp",
   "$_gm/image.cpp",
   "$_gm/image_pict.cpp",