builder/amazonebs: If cancelled, don't return artifact

builder/amazonebs/builder.go

@@ -102,6 +102,14 @@ func (b *Builder) Run(ui packer.Ui, hook packer.Hook) packer.Artifact {
 	b.runner = &multistep.BasicRunner{Steps: steps}
 	b.runner.Run(state)
 
+	// If we were cancelled, then return no artifacts
+	if raw, ok := state["cancelled"]; ok {
+		cancelled := raw.(bool)
+		if cancelled {
+			return nil
+		}
+	}
+
 	// Build the artifact and return it
 	return &artifact{state["amis"].(map[string]string)}
 }