Allow stripped_multiline_input to correctly handle the null from cancelling, which is handled upstream. This prevents the field from being cleared on cancel due to html_encode changing the null to an empty string. (#30188)

Also added newline per current .editorconfig

code/__HELPERS/text.dm

@@ -63,6 +63,8 @@
 	if(no_trim)
 		return copytext(html_encode(name), 1, max_length)
 	else
+		if(isnull(name))
+			return null
 		return trim(html_encode(name), max_length)
 
 //Runs byond's sanitization proc along-side strip_html_simple