[fix] 'unnecessary-dict-index-lookup' for in-loop deletetion

Closes #10726

Author: Pierre-Sassoulas

doc/whatsnew/fragments/10726.bugfix

@@ -0,0 +1,4 @@
+Fixed a crash in ``unnecessary-dict-index-lookup`` when the index of an enumerated list
+was deleted inside a for loop.
+
+Closes #10726

pylint/checkers/refactoring/refactoring_checker.py

@@ -2355,10 +2355,10 @@ def _check_unnecessary_list_index_lookup(
                         or iterating_object_name != subscript.value.as_string()
                     ):
                         continue
-
                     if (
                         isinstance(node, nodes.For)
-                        and index.lookup(index.name)[1][-1].lineno > node.lineno
+                        and (lookup_results := index.lookup(index.name)[1])
+                        and lookup_results[-1].lineno > node.lineno
                     ):
                         # Ignore this subscript if it has been redefined after
                         # the for loop.

tests/functional/r/regression_02/regression_10627.py

@@ -0,0 +1,5 @@
+"""Test for deleted index."""
+def test_deleted_index(letters: list[str]) -> None:
+    for index, letter in enumerate(letters):
+        del index
+        print(letters[index])