fix: prevent crashes from SVG rendering

[hammerlink]

When rendering certain SVGs, resvg::render can panic because resvg uses several assert! calls internally. This caused application crashes in Cosmic Desktop: pop-os/cosmic-epoch#2452

This patch wraps the render call in std::panic::catch_unwind. If resvg panics, the panic is caught and None is returned instead of crashing the app.

Example problematic SVG:

<svg xmlns="http://www.w3.org/2000/svg" width="100" height="100">                                                    
  <defs>                                                                                                             
    <filter id="specular" width="50" height="50">                                              
      <feSpecularLighting result="specular" lighting-color="white"                                                   
                          x="10" y="10" width="5" height="5">                                                        
        <fePointLight x="50" y="50" z="200"/>                                                                        
      </feSpecularLighting>                                                                                          
    </filter>                                                                                                        
  </defs>                                                                                                            
  <rect width="100" height="100" fill="blue" filter="url(#specular)"/>                                               
</svg>