Small redundancy fix (allocated intervals are never empty)

include/tiny-cuda-nn/gpu_memory.h

@@ -386,19 +386,14 @@ struct Interval {
 	// Inclusive start, exclusive end
 	size_t start, end;
 
-	/*
 	bool operator<(const Interval& other) const {
-		return end < other.end;
-	}*/
-
-
-	bool operator<(const Interval& other) const {
-		if(end < other.end)
-			return 1;
-		else if (end == other.end)
+		if (end < other.end) {
+			return true;
+		} else if (end == other.end) {
 			return start < other.start;
-		else
-			return 0;
+		} else {
+			return false;
+		}
 	}
 
 	bool overlaps(const Interval& other) const {
@@ -522,11 +517,11 @@ class GPUMemoryArena {
 
 		Interval interval = {start, m_allocated_intervals[start]};
 		m_allocated_intervals.erase(start);
-		if(interval.start != interval.end)
-			m_free_intervals.insert(
-				std::upper_bound(std::begin(m_free_intervals), std::end(m_free_intervals), interval),
-				interval
-			);
+
+		m_free_intervals.insert(
+			std::upper_bound(std::begin(m_free_intervals), std::end(m_free_intervals), interval),
+			interval
+		);
 
 		merge_adjacent_intervals();
 	}