Restarting a promoted build loses target environment

[JeffDownie]

When I try to restart a build that has been run as the result of a promotion, drone seems to trigger a new promotion build, but with the variable set to empty - for example, if I run

drone build promote my/repository 123 production

It works fine, but when I hit the restart button in the UI for this build, it does something roughly the equivalent of

drone build promote my/repository 123

(after the 123 intentionally left blank)

[bradrydzewski]

this can be fixed by modifying the code here.

			Sender:       prev.Sender,
			Params:       map[string]string{},
		}

+		for k, v := range prev.Params {
+			hook.Params[k] = v
+		}

[bradrydzewski]

fixed by c7788c4