Fix HTML unparsing when there's no entities

pyrogram/parser/html.py

@@ -233,6 +233,7 @@ class HTML:
         while i < len(entities):
             i += recursive(i)
 
+        if entities_offsets:
             last_offset = entities_offsets[-1][1]
             # no need to sort, but still add entities starting from the end
             for entity, offset in reversed(entities_offsets):

tests/parser/test_html.py

@@ -137,3 +137,11 @@ def test_html_unparse_escaped_nested():
          pyrogram.types.MessageEntity(type=pyrogram.enums.MessageEntityType.UNDERLINE, offset=8, length=16)])
 
     assert HTML.unparse(text=text, entities=entities) == expected
+
+
+def test_html_unparse_no_entities():
+    expected = "text"
+    text = "text"
+    entities = []
+
+    assert HTML.unparse(text=text, entities=entities) == expected