From f7ec14e166325cf4aee63587c6d9d4019da00a99 Mon Sep 17 00:00:00 2001
From: taizan-hokuto <55448286+taizan-hokuto@users.noreply.github.com>
Date: Fri, 22 May 2020 02:27:52 +0900
Subject: [PATCH] Fix for #7

---
 pytchat/tool/extract/duplcheck.py | 9 ++++++---
 pytchat/tool/extract/extractor.py | 9 +++++----
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/pytchat/tool/extract/duplcheck.py b/pytchat/tool/extract/duplcheck.py
index 2504e59..e94c011 100644
--- a/pytchat/tool/extract/duplcheck.py
+++ b/pytchat/tool/extract/duplcheck.py
@@ -70,7 +70,8 @@ def check_duplicate_offset(chatdata):
         if is_duplicate(i,i+1)]
 
 def remove_duplicate_head(blocks):
-    if len(blocks) == 1 : return blocks
+    if len(blocks) == 0 or len(blocks) == 1:
+        return blocks
 
     def is_duplicate_head(index):
 
@@ -97,7 +98,8 @@ def remove_duplicate_head(blocks):
     return ret
 
 def remove_duplicate_tail(blocks):
-    if len(blocks) == 1 : return blocks    
+    if len(blocks) == 0 or len(blocks) == 1:
+        return blocks    
 
     def is_duplicate_tail(index):
         if len(blocks[index].chat_data) == 0:
@@ -126,7 +128,8 @@ def remove_overlap(blocks):
     Align the last offset of each block to the first offset 
     of next block (equals `end` offset of each block).
     """
-    if len(blocks) == 1 : return blocks
+    if len(blocks) == 0 or len(blocks) == 1:
+        return blocks    
 
     for block in blocks:
         if block.is_last:
diff --git a/pytchat/tool/extract/extractor.py b/pytchat/tool/extract/extractor.py
index 8052cd5..b3721b9 100644
--- a/pytchat/tool/extract/extractor.py
+++ b/pytchat/tool/extract/extractor.py
@@ -40,10 +40,11 @@ class Extractor:
         return self
 
     def _set_block_end(self):
-        for i in range(len(self.blocks)-1):
-            self.blocks[i].end = self.blocks[i+1].first
-        self.blocks[-1].end = self.duration*1000
-        self.blocks[-1].is_last =True
+        if len(self.blocks) > 0:
+            for i in range(len(self.blocks)-1):
+                self.blocks[i].end = self.blocks[i+1].first
+            self.blocks[-1].end = self.duration*1000
+            self.blocks[-1].is_last =True
         return self
 
     def _remove_overlap(self):