[BUG] may be an out-of-boundary bug as a result of lack of necessary argument checks

[secsys-go]

Describe the bug
We used the Fuzz engine to modify some Test(TestUseRouterParentDisallow) data, and then the following crash appeared. We hope to get the help of the developer to confirm whether it is a real bug.

To Reproduce

app := iris.New()
app.PartyFunc("", func(p iris.Party) {})

Crash Log

panic: runtime error: index out of range [0] with length 0 [recovered]
	panic: runtime error: index out of range [0] with length 0

goroutine 10 [running]:
testing.tRunner.func1.2({0xc4c5c0, 0xc00045a2a0})
	D:/.../go1.20/src/testing/testing.go:1526 +0x24e
testing.tRunner.func1()
	D:/.../go1.20/src/testing/testing.go:1529 +0x39f
panic({0xc4c5c0, 0xc00045a2a0})
	D:/.../go1.20/src/runtime/panic.go:884 +0x213
github.com/kataras/iris/v12/core/router.(*APIBuilder).Party(0xc0001210e0, {0x0, 0x0}, {0x0, 0x0, 0x0})
	D:/.../iris/core/router/api_builder.go:846 +0x8f1
github.com/kataras/iris/v12/core/router.(*APIBuilder).PartyFunc(0xc0312d6078?, {0x0?, 0xc000097f60?}, 0xd4ab18)
	D:/.../iris/core/router/api_builder.go:924 +0x2a
github.com/kataras/iris/v12/core/router_test.TestUseRouterParentDisallow_POC(0x0?)
	D:/.../iris/core/router/TestUseRouterParentDisallow_POC_test.go:25 +0x2c
testing.tRunner(0xc0004829c0, 0xd4ab20)
	D:/.../go1.20/src/testing/testing.go:1576 +0x10b
created by testing.(*T).Run
	D:/.../go1.20/src/testing/testing.go:1629 +0x3ea

Expected behavior
Crash should not happen.

Desktop:

• OS: Windows 10

iris.Version

• commit 24ba4e8

[kataras]

Hello @secsys-go, this was expected, I modified the code so if empty relative path is given is translated to "/" now. However, we don't use this empty path anywhere in our documentation or examples.