fix: handle "-" output filename to write to stdout

merge_srt.py

@@ -166,6 +166,14 @@ if __name__ == '__main__':
                 'text': entry2['text'],
             })
 
-    with open(output_filename, 'w', encoding='utf-8') as f:
+    if output_filename == '-':
+        out = sys.stdout
+    else:
+        out = open(output_filename, 'w', encoding='utf-8')
+
+    try:
         for i, entry in enumerate(output, start=1):
-            f.write(f"{i}\n{entry['timestamp']}\n{entry['text'].strip()}\n\n")
+            out.write(f"{i}\n{entry['timestamp']}\n{entry['text'].strip()}\n\n")
+    finally:
+        if out is not sys.stdout:
+            out.close()