fix for overflowing tree

Author: willmcgugan

src/textual/widgets/_tree.py

@@ -788,6 +788,7 @@ def get_guides(style: Style) -> tuple[str, str, str, str]:
             self._line_cache[cache_key] = segments
 
         segments = line_crop(segments, x1, x2, width)
+        segments = Segment.adjust_line_length(segments, width)
 
         return segments