Fix the render-task displaying the wrong time after being paused or/and saved

BlueMapSponge/src/main/java/de/bluecolored/bluemap/sponge/RenderManager.java

@@ -94,6 +94,11 @@ public class RenderManager {
 	public boolean prioritizeRenderTask(RenderTask renderTask) {
 		synchronized (renderTasks) {
 			if (renderTasks.remove(renderTask)) {
+				
+				//pause first task
+				RenderTask currentFirst = renderTasks.peek();
+				if (currentFirst != null) currentFirst.pause();
+				
 				renderTasks.addFirst(renderTask);
 				return true;
 			}

BlueMapSponge/src/main/java/de/bluecolored/bluemap/sponge/RenderTask.java

@@ -104,6 +104,8 @@ public class RenderTask {
 	 * It will resume as soon as a new ticket gets polled
 	 */
 	public void pause() {
+		if (firstTileTime < 0) return;
+		
 		synchronized (renderTiles) {
 			additionalRunTime += System.currentTimeMillis() - firstTileTime;
 			firstTileTime = -1;