VideoCommon: Add fallback handling for bounding box when disabled or unsupported

The SDK seems to write "default" bounding box values before every draw
(1023 0 1023 0 are the only values encountered so far, which happen to
be the extents allowed by the BP registers) to reset the registers for
comparison in the pixel engine, and presumably to detect whether GX has
updated the registers with real values. Handling these writes and
returning them on read when bounding box emulation is disabled or
unsupported, even without computing real values from rendering, seems
to prevent games from corrupting memory or crashing.

This obviously does not fix any effects that rely on bounding box
emulation, but having the game not clobber its own code/data or just
outright crash is a definite improvement.

Source/Core/VideoCommon/RenderBase.h

@@ -394,6 +394,18 @@ private:
   u32 m_last_xfb_stride = 0;
   u32 m_last_xfb_height = 0;
 
+  // Nintendo's SDK seems to write "default" bounding box values before every draw (1023 0 1023 0
+  // are the only values encountered so far, which happen to be the extents allowed by the BP
+  // registers) to reset the registers for comparison in the pixel engine, and presumably to detect
+  // whether GX has updated the registers with real values.
+  //
+  // We can store these values when Bounding Box emulation is disabled and return them on read,
+  // which the game will interpret as "no pixels have been drawn"
+  //
+  // This produces much better results than just returning garbage, which can cause games like
+  // Ultimate Spider-Man to crash
+  std::array<u16, 4> m_bounding_box_fallback = {};
+
   // NOTE: The methods below are called on the framedumping thread.
   void FrameDumpThreadFunc();
   bool StartFrameDumpToFFMPEG(const FrameDump::FrameData&);