Fix nil pointer dereference cause by accessing the last used input without checking its existence

config.go

@@ -21,7 +21,7 @@ const configFile = "config.toml"
 
 func initializeConfigIfNot() {
 	log.Println("Checking if config needs to be initialized")
-	conf := config{Threshold: 95, DisplayMonitorSources: false, EnableUpdates: true} // if you're a package maintainer and you mess with this, we have a problem.
+	conf := config{Threshold: 95, DisplayMonitorSources: false, EnableUpdates: true, LastUsedInput: nil} // if you're a package maintainer and you mess with this, we have a problem.
 	// Unless you set -tags release on the build the updater is *not* compiled in any. DO NOT MESS WITH THIS!
 	// This isn't and never was the proper location to disable the updater.
 

main.go

@@ -246,9 +246,12 @@ func getSourcesWithPreSelectedInput(ctx *ntcontext) []input {
 	inputs := getSources(ctx.paClient)
 	preselectedInputId := ctx.config.LastUsedInput
 	inputExists := false
-	for _, input := range inputs {
-		inputExists = inputExists || input.ID == *preselectedInputId
+	if preselectedInputId != nil {
+		for _, input := range inputs {
+			inputExists = inputExists || input.ID == *preselectedInputId
+		}
 	}
+
 	if !inputExists {
 		defaultSource, err := getDefaultSourceID(ctx.paClient)
 		if err != nil {