[System Test][XDCR] panic: runtime error: invalid memory address or nil pointer dereference

-test tests/integration/neo/test_neo_couchstore_milestone2.yml -scope tests/integration/neo/scope_couchstore.yml

2021-10-20T15:22:24.667-07:00, ns_log:0:info:message(ns_1@172.23.97.121) - Service 'goxdcr' exited with status 2. Restarting. Messages:

net/http.(*response).write(0x10c14bf5e380, 0x1004, 0x10c014c82600, 0x1004, 0x1004, 0x0, 0x0, 0xb81540, 0xd7ea88, 0x0)

	/home/couchbase/.cbdepscache/exploded/x86_64/go-1.16.5/go/src/net/http/server.go:1615 +0x38a

net/http.(*response).Write(0x10c14bf5e380, 0x10c014c82600, 0x1004, 0x1004, 0x10c089a8fd68, 0x2, 0x2)

	/home/couchbase/.cbdepscache/exploded/x86_64/go-1.16.5/go/src/net/http/server.go:1573 +0x56

github.com/couchbase/goxdcr/adminport.(*httpServer).systemHandler.func2(0x10c14c2c1200, 0x10c0d146b7b0)

	/home/couchbase/jenkins/workspace/couchbase-server-unix/goproj/src/github.com/couchbase/goxdcr/adminport/admin_httpd.go:149 +0x5be

github.com/couchbase/goxdcr/base.ExecWithTimeout.func1(0x10c14c3a2ea0, 0x10c14c2c12c0)

	/home/couchbase/jenkins/workspace/couchbase-server-unix/goproj/src/github.com/couchbase/goxdcr/base/simple_utils.go:47 +0x27

created by github.com/couchbase/goxdcr/base.ExecWithTimeout

	/home/couchbase/jenkins/workspace/couchbase-server-unix/goproj/src/github.com/couchbase/goxdcr/base/simple_utils.go:46 +0x99

2021-10-20T15:22:22.811-07:00 ERRO GOXDCR.CheckpointSvc: Unable to GC brokenmapping cache - Unable to clean broken mappings for dcdab404d80fabf11a1a57b7534db21d/bucket4/bucket4 due to concurrent ongoing upsert operation

2021-10-20T15:22:22.836-07:00 [WARN] failed to transmit command UPR_NOOP. Error write tcp4 172.23.97.121:57046->172.23.97.121:11210: write: broken pipe 

2021-10-20T15:22:22.841-07:00 INFO GOXDCR.CheckpointMgr: Checkpointing for MainPipeline replication dcdab404d80fabf11a1a57b7534db21d/bucket4/bucket4, vb_list=[43 95 105 106 113 114 115 116 117 118 119 120 121 130 147 274 320 321 322 323 324 325 326 354 429 430 431 432 433 434 435 442 444 445 446 447 448 449 450 451 464 465 466 467 468 469 470 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 564 609 610 611 615 731 732], time_to_wait=10m0s, interval_btwn_vb=7.058 sec

panic: runtime error: invalid memory address or nil pointer dereference

[signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0x56ccb0]

goroutine 20500110 [running]:

bufio.(*Writer).Available(...)

	/home/couchbase/.cbdepscache/exploded/x86_64/go-1.16.5/go/src/bufio/bufio.go:624

bufio.(*Writer).Write(0x0, 0x132eeb0, 0x2, 0x2, 0xc909ab, 0x7, 0x10c14bf5e424)

	/home/couchbase/.cbdepscache/exploded/x86_64/go-1.16.5/go/src/bufio/bufio.go:634 +0x70

net/http.(*chunkWriter).writeHeader(0x10c14bf5e3c0, 0x10c014c82600, 0x1004, 0x1004)

	/home/couchbase/.cbdepscache/exploded/x86_64/go-1.16.5/go/src/net/http/server.go:1487 +0x985

net/http.(*chunkWriter).Write(0x10c14bf5e3c0, 0x10c014c82600, 0x1004, 0x1004, 0x6e67e9, 0x10c13d9029e8, 0x10c16e95edf0)

	/home/couchbase/.cbdepscache/exploded/x86_64/go-1.16.5/go/src/net/http/server.go:370 +0x2e7

bufio.(*Writer).Write(0x10c127245640, 0x10c014c82600, 0x1004, 0x1004, 0x243022, 0x243022, 0x43da1c)

	/home/couchbase/.cbdepscache/exploded/x86_64/go-1.16.5/go/src/bufio/bufio.go:639 +0x13d

net/http.(*response).write(0x10c14bf5e380, 0x1004, 0x10c014c82600, 0x1004, 0x1004, 0x0, 0x0, 0xb81540, 0xd7ea88, 0x0)

	/home/couchbase/.cbdepscache/exploded/x86_64/go-1.16.5/go/src/net/http/server.go:1615 +0x38a

net/http.(*response).Write(0x10c14bf5e380, 0x10c014c82600, 0x1004, 0x1004, 0x10c089a8fd68, 0x2, 0x2)

	/home/couchbase/.cbdepscache/exploded/x86_64/go-1.16.5/go/src/net/http/server.go:1573 +0x56

github.com/couchbase/goxdcr/adminport.(*httpServer).systemHandler.func2(0x10c14c2c1200, 0x10c0d146b7b0)

	/home/couchbase/jenkins/workspace/couchbase-server-unix/goproj/src/github.com/couchbase/goxdcr/adminport/admin_httpd.go:149 +0x5be

github.com/couchbase/goxdcr/base.ExecWithTimeout.func1(0x10c14c3a2ea0, 0x10c14c2c12c0)

	/home/couchbase/jenkins/workspace/couchbase-server-unix/goproj/src/github.com/couchbase/goxdcr/base/simple_utils.go:47 +0x27

created by github.com/couchbase/goxdcr/base.ExecWithTimeout

	/home/couchbase/jenkins/workspace/couchbase-server-unix/goproj/src/github.com/couchbase/goxdcr/base/simple_utils.go:46 +0x99