fix vu creation races and atomic ratelimit deref

wasp/wasp.go

@@ -379,7 +379,9 @@ func (g *Generator) runExecuteLoop() {
 		for i := 0; i < int(vus); i++ {
 			inst := g.vu.Clone(g)
 			g.runVU(inst)
+			g.currentSegmentMu.Lock()
 			g.vus = append(g.vus, inst)
+			g.currentSegmentMu.Unlock()
 		}
 	}
 }
@@ -508,6 +510,7 @@ func (g *Generator) processSegment() bool {
 		if oldVUs == newVUs {
 			return false
 		}
+		g.currentSegmentMu.Lock()
 		if oldVUs > g.currentSegment.From {
 			for i := 0; i < vusToSpawn; i++ {
 				g.vus[i].Stop(g)
@@ -520,6 +523,7 @@ func (g *Generator) processSegment() bool {
 				g.vus = append(g.vus, inst)
 			}
 		}
+		g.currentSegmentMu.Unlock()
 	}
 	return false
 }
@@ -624,8 +628,10 @@ func (g *Generator) pacedCall() {
 	if !g.Stats().RunStarted.Load() {
 		return
 	}
-	l := *g.rl.Load()
-	l.Take()
+	if &g.rl == nil {
+		return
+	}
+	(*g.rl.Load()).Take()
 	if g.stats.RunPaused.Load() {
 		return
 	}