Optimize some if statements for tersity

The optimizations are done for tersity, hopefully maintaining readability.

src/csspring/selectors.py

@@ -62,10 +62,7 @@ def parse_any_value(input: TokenStream) -> Product | None:
             case None:
                 break
         result.append(token)
-    if result:
-        return result
-    else:
-        return None
+    return result or None
 
 @parse.register
 def _(production: CommaSeparatedRepetitionProduction, input: TokenStream) -> Product | None:
@@ -107,10 +104,7 @@ def _(production: ConcatenationProduction, input: TokenStream) -> Product | None
 def _(production: NonEmptyProduction, input: TokenStream) -> Product | None:
     """Variant of `parse` for productions of the `!` multiplier variety (see https://drafts.csswg.org/css-values-4/#mult-req)."""
     result = cast(Product, parse(production.element, input)) # The element of a non-empty production is concatenation, and the `parse` overload for `ConcatenationProduction` never returns a `Token`, only `Product | None`
-    if result and any(tokens(result)):
-        return result
-    else:
-        return None
+    return result if result and any(tokens(result)) else None
 
 @parse.register
 def _(production: ReferenceProduction, input: TokenStream) -> Product | Token | None: