markup syntax error throws parse exception, crashing entire webpack watch process

[elirov]

Describe the bug
Any html markup error in the component causes the parser to throw a fatal error, which crashes webpack watch, necessitating a full restart of the process.

Logs
ERROR in ./tmpls/patient-intake/components/sections/Insurance.svelte
Module build failed (from ./node_modules/svelte-loader/index.js):
ParseError: Unexpected token
at error (/Users/elirov/workspace/xdocs/node_modules/svelte/src/compiler/utils/error.ts:25:16)
at Parser$1.error (/Users/elirov/workspace/xdocs/node_modules/svelte/src/compiler/parse/index.ts:101:3)
at Parser$1.acorn_error (/Users/elirov/workspace/xdocs/node_modules/svelte/src/compiler/parse/index.ts:94:8)
at read_expression (/Users/elirov/workspace/xdocs/node_modules/svelte/src/compiler/parse/read/expression.ts:34:10)
at mustache (/Users/elirov/workspace/xdocs/node_modules/svelte/src/compiler/parse/state/mustache.ts:379:22)
at new Parser$1 (/Users/elirov/workspace/xdocs/node_modules/svelte/src/compiler/parse/index.ts:53:12)
at parse (/Users/elirov/workspace/xdocs/node_modules/svelte/src/compiler/parse/index.ts:218:17)
at compile (/Users/elirov/workspace/xdocs/node_modules/svelte/src/compiler/compile/index.ts:94:14)
at injectVarsToCode (/Users/elirov/workspace/xdocs/node_modules/svelte-preprocess/dist/transformers/typescript.js:71:45)
at mixedImportsTranspiler (/Users/elirov/workspace/xdocs/node_modules/svelte-preprocess/dist/transformers/typescript.js:225:26)
@ ./tmpls/patient-intake/components/NewPatientView.svelte 23:0-52 60:17-26 215:2-11
@ ./tmpls/patient-intake/components/MainLayout.svelte 25:0-53 164:22-36 661:2-16
@ ./tmpls/patient-intake/init.js 16:0-69 29:35-45
@ ./src/client/dev/main.js 10:0-61 17:2-16

webpack 5.64.4 compiled with 1 error in 8794 ms
node:internal/validators:120
throw new ERR_INVALID_ARG_TYPE(name, 'string', value);
^

TypeError: The "path" argument must be of type string. Received undefined
at new NodeError (node:internal/errors:371:5)
at validateString (node:internal/validators:120:11)
at Object.dirname (node:path:1276:5)
at WatcherManager.watchFile (/Users/elirov/workspace/xdocs/node_modules/watchpack/lib/getWatcherManager.js:30:26)
at /Users/elirov/workspace/xdocs/node_modules/watchpack/lib/watchpack.js:280:41
at Object.exports.batch (/Users/elirov/workspace/xdocs/node_modules/watchpack/lib/watchEventSource.js:326:3)
at Watchpack.watch (/Users/elirov/workspace/xdocs/node_modules/watchpack/lib/watchpack.js:278:20)
at NodeWatchFileSystem.watch (/Users/elirov/workspace/xdocs/node_modules/webpack/lib/node/NodeWatchFileSystem.js:107:16)
at Watching.watch (/Users/elirov/workspace/xdocs/node_modules/webpack/lib/Watching.js:325:48)
at /Users/elirov/workspace/xdocs/node_modules/webpack/lib/Watching.js:303:13 {
code: 'ERR_INVALID_ARG_TYPE'
}

To Reproduce
Create a svelte component with something like this in the markup section:
{if<div/>

Expected behavior
Should not throw a fatal error - just output anything so that the watch process can stay up (similarly to what happens if you have a syntax error in the <script> part of the svelte file.

• Your operating system: (e.x. OS X 10, Ubuntu Linux 19.10, Windows XP, etc)

• macos

• svelte-preprocess version (Please check you can reproduce the issue with the latest release!)

• 4.9.8

• Whether your project uses Webpack or Rollup

• webpack

[bfanger]

Fix available sveltejs/svelte-loader#199

[dummdidumm]

Thanks, closing in favor of that PR