when -> if

Co-authored-by: Lenz Weber-Tronic <lorenz.weber-tronic@apollographql.com>

Author: jerelmiller

docs/source/data/queries.mdx

@@ -377,7 +377,7 @@ If you need to reference the currently executed query's variables, use the `vari
 
 <Tip>
 
-The `variables` property is empty until the execution function is called for the first time. Use the `called` property returned by `useLazyQuery` to determine when the execution function has been called at least once.
+The `variables` property is empty until the execution function is called for the first time. Use the `called` property returned by `useLazyQuery` to determine if the execution function has been called at least once.
 
 </Tip>