Return 0 on EOF in burn_source.

libisofs/ecma119.c

@@ -876,7 +876,7 @@ bs_read_block(struct burn_source *bs)
 			t->curblock++;
 			return t->block_size;
 		}
-		return -1;
+		return 0;
 	}
 	if (t->state_data_valid)
 		write_data_chunk(t, t->buffer);
@@ -898,8 +898,8 @@ bs_read(struct burn_source *bs, unsigned char *buf, int size)
 			/* we need to read next block */
 			t->bytes_read = 0;
 			ret = bs_read_block(bs);
-			if (ret < 0)
-				return -1;
+			if (ret <= 0)
+				return ret;
 		}
 
 		int bytes_to_read = 2048 - t->bytes_read;