fix: convert pk from db to str. (#17876)

(cherry picked from commit 87972656d4)

Co-authored-by: Devin Slauenwhite <devin.slauenwhite@gmail.com>

frappe/core/doctype/data_import/importer.py

@@ -984,7 +984,9 @@ class Column:
 		if self.df.fieldtype == "Link":
 			# find all values that dont exist
 			values = list({cstr(v) for v in self.column_values[1:] if v})
-			exists = [d.name for d in frappe.db.get_all(self.df.options, filters={"name": ("in", values)})]
+			exists = [
+				cstr(d.name) for d in frappe.db.get_all(self.df.options, filters={"name": ("in", values)})
+			]
 			not_exists = list(set(values) - set(exists))
 			if not_exists:
 				missing_values = ", ".join(not_exists)