[librsvg: 5/9] gradient.rs: Log when referencing a nonexistent gradient

[Federico Mena Quintero <federico src gnome org>]

commit 4df98218fc333f147770d5650ce01cbae8824c46
Author: Federico Mena Quintero <federico gnome org>
Date:   Wed Oct 24 11:41:07 2018 -0500

    gradient.rs: Log when referencing a nonexistent gradient

 rsvg_internals/src/gradient.rs | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/rsvg_internals/src/gradient.rs b/rsvg_internals/src/gradient.rs
index 36b30e63..8d76c0e8 100644
--- a/rsvg_internals/src/gradient.rs
+++ b/rsvg_internals/src/gradient.rs
@@ -426,6 +426,8 @@ fn acquire_gradient<'a>(draw_ctx: &'a mut DrawingCtx<'_>, name: &str) -> Option<
         }
     }
 
+    rsvg_log!("element \"{}\" does not exist or is not a gradient", name);
+
     None
 }