CLN: making copies of targets and values (pandas-dev#35498)

Author: alexhlim

pandas/_libs/index.pyx

@@ -278,6 +278,8 @@ cdef class IndexEngine:
         targets_mask = isnaobj(targets)
         values_mask = isnaobj(values)
         if targets_mask.any():
+            targets_copy = targets.copy()
+            values_copy = values.copy()
             targets[targets_mask] = 0
             values[values_mask] = 0