Set last returned index to -1 when removing

src/main/kotlin/ru/dbotthepony/mc/otm/core/collect/BlockPosSet.kt

@@ -71,6 +71,7 @@ class BlockPosSet : MutableSet<BlockPos> {
 						throw NoSuchElementException()
 
 					bits[last] = false
+					last = -1
 				}
 			}
 		}
@@ -157,6 +158,7 @@ class BlockPosSet : MutableSet<BlockPos> {
 			override fun next(): BlockPos {
 				findNext()
 				last = current
+				foundNext = false
 				val blockPos = current.next()
 				return blockPos
 			}