Add error handling for nil RouteContext in URLFormat

[Taaipi]

Fix #839
Ref #718

In the current URLFormat middleware implementation, when rctx (Route Context) is nil, it could lead to unexpected behavior or panic errors in subsequent processing.

To avoid this, I have prioritized not allowing unexpected behavior by implementing error handling for the cases where rctx is missing or nil. Now, instead of failing silently or causing a panic error, the system will return a proper HTTP error response.

This change ensures that the system behaves consistently and avoids potential pitfalls that might arise from missing or improperly initialized rctx.