Deleting a Delivery Service created as a result of a Delivery Service Request results in Internal Server Error

[srijeet0406]

This Bug Report affects these Traffic Control components:

• Traffic Ops

Current behavior:

Run TO and TP.
Create a DSR and fulfill it.
Try deleting the resulting DS.
You will notice an ISE 500.

Expected behavior:

Deleting a DS created from a DSR should not give an ISE 500.

Steps to reproduce:

Create a DSR and fulfill it.
Then, try to delete the created DS.
You will see an internal server error with the following log lines in error.log:

ERROR: server.go:3170: http: superfluous response.WriteHeader call from github.com/apache/trafficcontrol/traffic_ops/traffic_ops_golang/routing/middleware.GzipResponse (wrappers.go:240)
ERROR: api.go:253: 2022-02-09T16:32:31.107982633Z: 10.234.97.13:40522 panic: (err: runtime error: invalid memory address or nil pointer dereference) stacktrace:
goroutine 5499473 [running]:
github.com/apache/trafficcontrol/lib/go-util.Stacktrace()
        /tmp/go/src/github.com/apache/trafficcontrol/lib/go-util/util.go:32 +0x66
github.com/apache/trafficcontrol/traffic_ops/traffic_ops_golang/routing/middleware.WrapPanicRecover.func1.1()
        /tmp/go/src/github.com/apache/trafficcontrol/traffic_ops/traffic_ops_golang/routing/middleware/wrappers.go:173 +0x66
panic({0xe000c0, 0x16ab940})
        /usr/local/go/src/runtime/panic.go:1038 +0x215
github.com/apache/trafficcontrol/traffic_ops/traffic_ops_golang/deliveryservice/request.PutAssignment({0x1079830, 0xc004c227b0}, 0xc001320c00)
        /tmp/go/src/github.com/apache/trafficcontrol/traffic_ops/traffic_ops_golang/deliveryservice/request/assign.go:226 +0xa8d
github.com/apache/trafficcontrol/traffic_ops/traffic_ops_golang/routing/middleware.RequiredPermissionsMiddleware.func1.1({0x1079830, 0xc004c227b0}, 0xc001320c00)
        /tmp/go/src/github.com/apache/trafficcontrol/traffic_ops/traffic_ops_golang/routing/middleware/wrappers.go:312 +0x4cf
github.com/apache/trafficcontrol/traffic_ops/traffic_ops_golang/routing/middleware.AuthBase.GetWrapper.func1.1({0x1079830, 0xc004c227b0}, 0xc001320c00)
        /tmp/go/src/github.com/apache/trafficcontrol/traffic_ops/traffic_ops_golang/routing/middleware/wrappers.go:127 +0x32d
github.com/apache/trafficcontrol/traffic_ops/traffic_ops_golang/routing/middleware.WrapPanicRecover.func1({0x1079830, 0xc004c227b0}, 0xf004a6)
        /tmp/go/src/github.com/apache/trafficcontrol/traffic_ops/traffic_ops_golang/routing/middleware/wrappers.go:177 +0x7e
github.com/apache/trafficcontrol/traffic_ops/traffic_ops_golang/routing/middleware.WrapHeaders.func1({0x107bdb0, 0xc0012aa9c0}, 0x6b769f)
        /tmp/go/src/github.com/apache/trafficcontrol/traffic_ops/traffic_ops_golang/routing/middleware/wrappers.go:157 +0x60d
net/http.HandlerFunc.ServeHTTP(0x1, {0x107bdb0, 0xc0012aa9c0}, 0x43ef45)
        /usr/local/go/src/net/http/server.go:2047 +0x2f
net/http.(*timeoutHandler).ServeHTTP.func1()
        /usr/local/go/src/net/http/server.go:3337 +0x7c
created by net/http.(*timeoutHandler).ServeHTTP
        /usr/local/go/src/net/http/server.go:3331 +0x465

goroutine 1 [chan receive, 11790 minutes]:
main.signalReloader({0x1079630, 0x1060770}, 0xc000375be0)
        /tmp/go/src/github.com/apache/trafficcontrol/traffic_ops/traffic_ops_golang/traffic_ops_golang.go:379 +0xc7
main.main()
        /tmp/go/src/github.com/apache/trafficcontrol/traffic_ops/traffic_ops_golang/traffic_ops_golang.go:236 +0x1253

goroutine 3 [select, 11790 minutes]:
database/sql.(*DB).connectionOpener(0xc00032e680, {0x1083738, 0xc00030c000})
        /usr/local/go/src/database/sql/sql.go:1196 +0x93