Given empty pathvariable value and get 500 internal server error

[LinhaoJiaTomo]

Describe the bug
We have an api like

@GetMapping("/xxx/{id}")
fun retrieveXxxById(@PathVariable id: String)

And when we call this api using /xxx and not give the PathVariable id, we'll get 500 error, this issue happens when we update our org.springdoc:springdoc-openapi-kotlin from 1.6.15 to 1.7.0, it used to throw 404 from our logic.
Our configuration of springdoc is

springdoc:
  webjars:
    prefix: ''
  swagger-ui:
    disable-swagger-default-url: true
    operationsSorter: method
    tagsSorter: alpha
  api-docs:
    enabled: true

And the exception detail is

java.lang.StringIndexOutOfBoundsException: String index out of range: -1
	at java.lang.String.substring(Unknown Source)
	Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException: 
Original Stack Trace:
		at java.lang.String.substring(Unknown Source)
		at org.springdoc.ui.AbstractSwaggerResourceResolver.path(AbstractSwaggerResourceResolver.java:71)
		at org.springdoc.ui.AbstractSwaggerResourceResolver.findWebJarResourcePath(AbstractSwaggerResourceResolver.java:42)
		at org.springdoc.webflux.ui.SwaggerResourceResolver.resolveResource(SwaggerResourceResolver.java:35)
		at org.springframework.web.reactive.resource.DefaultResourceResolverChain.resolveResource(DefaultResourceResolverChain.java:75)
		... 148 frames truncated

To Reproduce
Steps to reproduce the behavior:

• What version of spring-boot you are using?
  2.7.10
• What modules and versions of springdoc-openapi are you using?
  org.springdoc:springdoc-openapi-webflux-ui:1.7.0, org.springdoc:springdoc-openapi-kotlin:1.7.0

Expected behavior
Not return 500

[sanketmeghani]

I am also getting similar error while accessing /swagger-ui/.

[Martin01248]

I am also having this issue that /swagger-ui leads to StringIndexOutOfBoundsException: String index out of range: -1 resulting in 500 server error.

Class AbstractSwaggerResourceResolver
with method

	private String path(String webjar, String path) {
		if (path.startsWith(webjar)) {
			path = path.substring(webjar.length() + 1);
		}
		return path;
	}

where parameters are
webjar="swagger-ui"
path="swagger-ui"
results in
StringIndexOutOfBoundsException: String index out of range: -1

[uc4w6c]

i think this will fix it. #2244

[bnasslahsen]

Fixed by #2235