fix ut

Author: Hitenjain14

code/go/0chain.net/validatorcore/storage/models_test.go

@@ -572,6 +572,7 @@ func TestChallengeRequest_VerifyChallenge(t *testing.T) {
 				RandomNumber: int64(1),
 				AllocationID: "2",
 			},
+			alloc:      &storage.Allocation{},
 			wantErr:    true,
 			wantErrMsg: "Invalid write marker",
 		},
@@ -612,6 +613,7 @@ func TestChallengeRequest_VerifyChallenge(t *testing.T) {
 				RandomNumber: int64(1),
 				AllocationID: "1",
 			},
+			alloc:      &storage.Allocation{},
 			wantErr:    true,
 			wantErrMsg: "Invalid write marker",
 		},