More than one client can cause an issue on refresh

[ssoper]

Reproduce

• Have two tabs open to the same localhost url
• Save the file that url is pointing to, causing it to compile

Stacktrace

	at java.base/java.util.LinkedHashMap$LinkedHashIterator.nextNode(LinkedHashMap.java:719)
	at java.base/java.util.LinkedHashMap$LinkedEntryIterator.next(LinkedHashMap.java:751)
	at java.base/java.util.LinkedHashMap$LinkedEntryIterator.next(LinkedHashMap.java:749)
	at com.seansoper.zebec.ContentServer.refresh(ContentServer.kt:174)
	at com.seansoper.zebec.Core$watchFiles$3.invoke(Core.kt:75)Client z3044g connected via SSE
	at com.seansoper.zebec.Core$watchFiles$3.invoke(Core.kt:9)
	at com.seansoper.zebec.fileProcessor.EventHandler.process(EventHandler.kt:84)
	at com.seansoper.zebec.Core.watchFiles(Core.kt:68)
	at com.seansoper.zebec.Core$watchFiles$1.invokeSuspend(Core.kt)
	at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
	at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:56)
	at kotlinx.coroutines.EventLoopImplBase.processNextEvent(EventLoop.common.kt:271)
	at kotlinx.coroutines.BlockingCoroutine.joinBlocking(Builders.kt:79)
	at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking(Builders.kt:54)
	at kotlinx.coroutines.BuildersKt.runBlocking(Unknown Source)
	at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking$default(Builders.kt:36)
	at kotlinx.coroutines.BuildersKt.runBlocking$default(Unknown Source)
	at com.seansoper.zebec.Core.main(Core.kt:41)```