nullish srcset attribute crashes Svelte (4.0.2)

[vschoettke]

Describe the bug

Passing a srcset={null} or srcset={undefined} to an image results in a crash. In my case the srcset is generated with a function that returns undefined when the image is an SVG.

The problem only occurred after upgrading from Svelte 4.0.1 to 4.0.2.

Probably introduced with #8838, but I wonder why the srcset_url_equal function is called anyway when the srcset is nullish.

Reproduction

I a repl for reproducing the error here:

https://svelte.dev/repl/4e3cac66da884b7dbe88d988fc9edcc7?version=4.0.2

You can see
"Cannot read properties of null (reading 'split')" in the bottom right.

Logs

TypeError: Cannot read properties of undefined (reading 'split') at split_srcset
(http://localhost:5173/node_modules/.vite/deps/chunk-WHDRF6EJ.js?v=1735e15a:55:17) at srcset_url_equal 
(http://localhost:5173/node_modules/.vite/deps/chunk-WHDRF6EJ.js?v=1735e15a:59:16) at Object.hydrate [as h]

System Info

System:
    OS: macOS 12.6.7
    CPU: (10) arm64 Apple M1 Pro
    Memory: 137.28 MB / 16.00 GB
    Shell: 3.2.57 - /bin/sh
  Binaries:
    Node: 18.16.0 - ~/.nvm/versions/node/v18.16.0/bin/node
    Yarn: 1.22.19 - ~/.nvm/versions/node/v18.16.0/bin/yarn
    npm: 9.5.1 - ~/.nvm/versions/node/v18.16.0/bin/npm
  Browsers:
    Chrome: 114.0.5735.198
    Safari: 16.5.1
  npmPackages:
    svelte: ^4.0.2 => 4.0.2

Severity

blocking an upgrade