Improve placement logic to ensure it takes into account the case wher…

…e known leads to non existant section

isort/place.py

@@ -54,7 +54,7 @@ def _known_pattern(name: str, config: Config) -> Optional[Tuple[str, str]]:
     module_names_to_check = (".".join(parts[:first_k]) for first_k in range(len(parts), 0, -1))
     for module_name_to_check in module_names_to_check:
         for pattern, placement in config.known_patterns:
-            if pattern.match(module_name_to_check):
+            if placement in config.sections and pattern.match(module_name_to_check):
                 return (placement, f"Matched configured known pattern {pattern}")
 
     return None