[librsvg] with_discrete_layer(): Propagate errors from cairo::ImageSurface::create()

[Federico Mena Quintero <federico src gnome org>]

commit 1b1fba9d3aabd24ce905e87d16b99283410fe58c
Author: Federico Mena Quintero <federico gnome org>
Date:   Sun Sep 23 18:56:31 2018 -0500

    with_discrete_layer(): Propagate errors from cairo::ImageSurface::create()
    
    This is the second part of #345.

 rsvg_internals/src/drawing_ctx.rs                  | 2 +-
 tests/fixtures/render-crash/345-too-large-size.svg | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/rsvg_internals/src/drawing_ctx.rs b/rsvg_internals/src/drawing_ctx.rs
index c34b2490..01c21b17 100644
--- a/rsvg_internals/src/drawing_ctx.rs
+++ b/rsvg_internals/src/drawing_ctx.rs
@@ -405,7 +405,7 @@ impl<'a> DrawingCtx<'a> {
                     cairo::Format::ARgb32,
                     self.rect.width as i32,
                     self.rect.height as i32,
-                ).unwrap();
+                )?;
 
                 if filter.is_some() {
                     self.surfaces_stack.push(surface.clone());
diff --git a/tests/fixtures/render-crash/345-too-large-size.svg 
b/tests/fixtures/render-crash/345-too-large-size.svg
new file mode 100644
index 00000000..bc5cfde2
--- /dev/null
+++ b/tests/fixtures/render-crash/345-too-large-size.svg
@@ -0,0 +1,3 @@
+<svg>
+  <path d="M0,0 L1,0 L100000,100000" style="opacity:0"/>
+</svg>