Update docs/platforms/rust/common/configuration/options.mdx

Author: lcian

docs/platforms/rust/common/configuration/options.mdx

@@ -107,7 +107,7 @@ The default value of `MaxRequestBodySize::Medium` will capture request bodies up
 
 <SdkOption name="before_send" type='Fn'>
 
-This function is called with the event payload, and can return a modified event object, or `null` to skip reporting the event. This can be used, for instance, for manual PII stripping before sending.
+This function is called with the event payload, and can return a modified event object, or `None` to skip reporting the event. This can be used, for instance, for manual PII stripping before sending.
 
   By the time `before_send` is executed, all scope data has already been applied to the event. Further modification of the scope won't have any effect.