Use 0-length slice instead of nil to keep capacities

internal/buffered/command.go

@@ -59,6 +59,6 @@ func flushDelayedCommands() bool {
 	for _, c := range delayedCommands {
 		c.f()
 	}
-	delayedCommands = nil
+	delayedCommands = delayedCommands[:0]
 	return true
 }

internal/graphicscommand/command.go

@@ -269,7 +269,7 @@ func (q *commandQueue) Flush() {
 		q.commands = q.commands[nc:]
 	}
 	theGraphicsDriver.End()
-	q.commands = nil
+	q.commands = q.commands[:0]
 	q.nvertices = 0
 	q.nindices = 0
 	q.tmpNumIndices = 0