don't duplicate filename issues

contracts/management/commands/import_old_contracts.py

@@ -1081,6 +1081,8 @@ class Command(BaseCommand):
 
                             continue
 
+                        at_least_one_incorrect_filename = False
+
                         for file_key, file_value in file_data.items():
                             file_key = file_key.strip()
 
@@ -1090,6 +1092,8 @@ class Command(BaseCommand):
                             if not isinstance(file_value, str):
                                 observed_issues_count += 1
                                 contract.notes += f"Špatně zadaný název souboru {file_key}: {file_value}.\n"
+
+                                if not at_least_one_incorrect_filename:
                                     issues.append(
                                         self.use_issue("Neplatný název souboru")
                                     )
@@ -1101,6 +1105,8 @@ class Command(BaseCommand):
                                         )
                                     )
 
+                                at_least_one_incorrect_filename = True
+
                                 continue
 
                             file_path = os.path.join(contract_root, file_value)