fix error with selection when widget removed

Author: willmcgugan

src/textual/screen.py

@@ -1663,12 +1663,15 @@ def _watch__select_end(
         if end_region.y <= start_region.bottom or self._box_select:
             select_regions.append(Region.union(start_region, end_region))
         else:
-            container_region = Region.from_union(
-                [
-                    start_widget.select_container.content_region,
-                    end_widget.select_container.content_region,
-                ]
-            )
+            try:
+                container_region = Region.from_union(
+                    [
+                        start_widget.select_container.content_region,
+                        end_widget.select_container.content_region,
+                    ]
+                )
+            except NoMatches:
+                return
 
             start_region = Region.from_corners(
                 start_region.x,

src/textual/widget.py

@@ -1756,7 +1756,6 @@ def validate_scroll_target_x(self, value: float) -> float:
         return round(clamp(value, 0, self.max_scroll_x))
 
     def validate_scroll_y(self, value: float) -> float:
-        # return value
         return clamp(value, 0, self.max_scroll_y)
 
     def validate_scroll_target_y(self, value: float) -> float: