[SDL] Fixing SDL_UnlockSurface in IE10/IE11.

Previously, just calling SDL_UnlockSurface in IE10/IE11 would throw an exception, since Emscripten assumed that the ImageData's `data` property was Uint8ClampedArray, which has a backing buffer.

IE10/IE11 still uses the deprecated CanvasPixelArray, which does not have a backing buffer property:
https://developer.mozilla.org/en-US/docs/Web/API/CanvasPixelArray

I've added an additional path to SDL_UnlockSurface for these browsers.

1 files changed, 2 insertions, 0 deletions

diff --git a/tests/sdl_canvas.c b/tests/sdl_canvas.c
index 6bd659b8..cab48985 100644
--- a/tests/sdl_canvas.c
+++ b/tests/sdl_canvas.c
@@ -62,6 +62,8 @@ int main(int argc, char **argv) {
 
   printf("you should see two lines of text in different colors and a blue rectangle\n");
 
+  SDL_UnlockSurface(screen);
+  
   SDL_Quit();
 
   printf("done.\n");