resvg_render() (C wrapper function) does not crash on incorrect input

[geometer]

Using the library in our C++ project via C wrappers, we found that the app crashes if SVG data are incorrect. E.g, contain extra chars after closing the root <svg> tag. The patch fixes that issue by catching a panic instead of throwing it into C++ code (where catching is impossible).

[LaurenzV]

I think the right fix for this is to fix the crash in the Rust version instead? What file are you having problems with, and what is the backtrace?

[RazrFalcon]

Catching panics is probably a good idea, but you are checking for tree.is_null() twice. That's not needed.
Also, the code/API is expected to fail/abort on invalid arguments, so that's should stay as before.
Basically, only std::panic::catch_unwind is needed here.
But if we're adding std::panic::catch_unwind - we have to add it to all function that can panic, not just render one.

And yes, we should also fix the cause of the crash, not just handling of it.