Fix having multiple starbound clients being broken

src/main/kotlin/ru/dbotthepony/kstarbound/client/StarboundClient.kt

@@ -104,7 +104,7 @@ class StarboundClient : Closeable {
 
 	var fullbright = true
 
-	var gameTerminated = false
+	var clientTerminated = false
 		private set
 
 	/**
@@ -156,6 +156,8 @@ class StarboundClient : Closeable {
 		lock.lock()
 
 		try {
+			clients++
+
 			if (!glfwInitialized) {
 				check(GLFW.glfwInit()) { "Unable to initialize GLFW" }
 				glfwInitialized = true
@@ -991,21 +993,30 @@ class StarboundClient : Closeable {
 	}
 
 	override fun close() {
-		if (gameTerminated)
+		if (clientTerminated)
 			return
 
-		if (window != MemoryUtil.NULL) {
-			Callbacks.glfwFreeCallbacks(window)
-			GLFW.glfwDestroyWindow(window)
-		}
+		lock.lock()
 
-		GLFW.glfwTerminate()
-		GLFW.glfwSetErrorCallback(null)?.free()
+		try {
+			if (window != MemoryUtil.NULL) {
+				Callbacks.glfwFreeCallbacks(window)
+				GLFW.glfwDestroyWindow(window)
+			}
 
-		gameTerminated = true
+			if (--clients == 0) {
+				GLFW.glfwTerminate()
+				GLFW.glfwSetErrorCallback(null)?.free()
+				glfwInitialized = false
+			}
 
-		for (callback in terminateCallbacks) {
-			callback.invoke()
+			clientTerminated = true
+
+			for (callback in terminateCallbacks) {
+				callback.invoke()
+			}
+		} finally {
+			lock.unlock()
 		}
 	}
 
@@ -1021,6 +1032,8 @@ class StarboundClient : Closeable {
 		private val lock = ReentrantLock()
 		@Volatile
 		private var glfwInitialized = false
+		@Volatile
+		private var clients = 0
 
 		@JvmStatic
 		fun readInternal(file: String): String {