fix byte overflow when defragmenting chunks with more than 520KB of data

src/main/java/net/querz/mcaselector/io/mca/MCAFile.java

@@ -156,12 +156,12 @@ public void deFragment(File dest) throws IOException {
 			// loop over all offsets, readHeader the raw byte data (complete sections) and write it to new file
 			for (int i = 0; i < offsets.length; i++) {
 				// don't do anything if this chunk is empty
-				if (offsets[i] == 0 || sectors[i] <= 0) {
+				if (offsets[i] == 0 || sectors[i] == 0) {
 					skippedChunks++;
 					continue;
 				}
 
-				int sectors = this.sectors[i];
+				int sectors = this.sectors[i] & 0xFF;
 
 				// write offset and sector size to tmp file
 				rafTmp.seek(i * 4L);