Fix Tiny v2 serialization of missing lvt row indices

Author: Player3324

src/main/java/net/fabricmc/mappingio/format/Tiny2Writer.java

@@ -132,7 +132,7 @@ public boolean visitMethodVar(int lvtRowIndex, int lvIndex, int startOpIdx, Stri
 		writeTab();
 		write(startOpIdx);
 		writeTab();
-		if (lvtRowIndex >= 0) write(lvtRowIndex);
+		write(Math.max(lvtRowIndex, -1));
 		writeTab();
 		if (srcName != null) writeName(srcName);