Hopefully fix a rare concurrency issue in buffer Builder

core/src/main/java/com/seibel/distanthorizons/core/dataObjects/render/bufferBuilding/ColumnRenderBufferBuilder.java

@@ -163,6 +163,12 @@ public class ColumnRenderBufferBuilder
 					// get adjacent render data columns //
 					//==================================//
 					
+					// clear the old data so we can handle if one of the adjacent columns is missing/empty
+					adjColumnViews[EDhDirection.NORTH.compassIndex].clear();
+					adjColumnViews[EDhDirection.SOUTH.compassIndex].clear();
+					adjColumnViews[EDhDirection.EAST.compassIndex].clear();
+					adjColumnViews[EDhDirection.WEST.compassIndex].clear();
+					
 					for (EDhDirection direction : EDhDirection.CARDINAL_COMPASS)
 					{
 						try

core/src/main/java/com/seibel/distanthorizons/core/dataObjects/render/columnViews/ColumnRenderView.java

@@ -111,6 +111,14 @@ public final class ColumnRenderView implements AutoCloseable
 		}
 	}
 	
+	public void clear()
+	{
+		this.data = null;
+		this.size = 0;
+		this.offset = 0;
+		this.maxVerticalSliceCount = 0;
+	}
+	
 	//endregion
 	
 	
@@ -131,7 +139,7 @@ public final class ColumnRenderView implements AutoCloseable
 			// we can fairly confidently say this is a concurrent exception over an actual
 			// index out of bounds, since we're generally iterating over the whole
 			// array any time we use this getter.
-			throw new ConcurrentModificationException("Potential concurrent modification detected. Make sure the parent ColumnRenderSource isn't being closed before the ColumnArrayView processing is complete.", e);
+			throw new ConcurrentModificationException("Potential concurrent modification detected. Make sure the parent ColumnRenderSource isn't being closed before the ColumnRenderView processing is complete.", e);
 		}
 	}
 	public void set(int index, long value) { this.data.set(index + this.offset, value); }

core/src/main/java/com/seibel/distanthorizons/core/render/QuadTree/LodRenderSection.java

@@ -325,9 +325,11 @@ public class LodRenderSection implements IDebugRenderable, AutoCloseable
 		{
 			if (!this.bufferUploadFutureRef.compareAndSet(future, null)
 				// if the old future is canceled then the future ref will be different and that's expected
-				&& !future.isCancelled())
+				&& !future.isCancelled()
+				// if the old future is already done, then we don't care about the ref being swapped
+				&& !future.isDone())
 			{
-				LOGGER.error("Buffer upload future ref changed for pos: ["+DhSectionPos.toString(this.pos)+"].");
+				LOGGER.warn("Buffer upload future ref changed for pos: ["+DhSectionPos.toString(this.pos)+"].");
 			}
 			
 			return null;