RHINENG-21276: fix sigsegv

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x1947adf]
goroutine 2826 [running]:
app/evaluator.updateSystemPlatform(0xc02658edb0, 0xc025dae3c0, 0xc02648bb30, 0x221, 0x0, 0x0)
        /go/src/app/evaluator/evaluate.go:534 +0x13f
app/evaluator.evaluateAndStore(0xc025dae3c0, 0xc025741b40, 0xc02612efc0)
        /go/src/app/evaluator/evaluate.go:469 +0x1b5
app/evaluator.evaluateWithVmaas(0xc025741b40, 0xc000560460?, 0xc025dae3c0?)
        /go/src/app/evaluator/evaluate.go:281 +0x25
app/evaluator.evaluateInDatabase({0x2358448, 0xc000560460}, 0xc02612efc0, {0xc02412d9e1, 0x24})
        /go/src/app/evaluator/evaluate.go:228 +0xa5
app/evaluator.Evaluate({0x2358448, 0xc000560460}, 0xc02612efc0, {0xc02412d9e1, 0x24}, {0xc000046391, 0x6})
        /go/src/app/evaluator/evaluate.go:144 +0x1e7
app/evaluator.runEvaluate.func1()
        /go/src/app/evaluator/evaluate.go:184 +0x6f
created by app/evaluator.runEvaluate in goroutine 103
        /go/src/app/evaluator/evaluate.go:183 +0x25d

Author: MichaelMraka

evaluator/evaluate.go

@@ -531,7 +531,9 @@ func updateSystemPlatform(tx *gorm.DB, system *models.SystemPlatform,
 	advisories SystemAdvisoryMap, installed, installable, applicable int) error {
 	tStart := time.Now()
 	defer utils.ObserveSecondsSince(tStart, evaluationPartDuration.WithLabelValues("system-update"))
-	defer utils.ObserveSecondsSince(*system.LastUpload, uploadEvaluationDelay)
+	if system.LastUpload != nil {
+		defer utils.ObserveSecondsSince(*system.LastUpload, uploadEvaluationDelay)
+	}
 	if system.LastEvaluation != nil {
 		defer utils.ObserveHoursSince(*system.LastEvaluation, twoEvaluationsInterval)
 	}