Adds an existential check in case no query vars are present in dbAuth invocation (#10204)

Author: cannikin

.changesets/10204.md

@@ -0,0 +1,8 @@
+- chore(dbAuth): restore behavior of checking whether a search query is present
+
+Previously dbAuth would check whether or not query string variables were
+present at all before invoking the proper function. During a refactor we
+updated this code to assume a query would *always* be present. Which it would be
+during normal browser behavior. But, we had a complaint from a user who relied
+on this optional check in one of their tests. So we're restoring the optional
+check here.

packages/auth-providers/dbAuth/api/src/DbAuthHandler.ts

@@ -1456,7 +1456,7 @@ export class DbAuthHandler<
   // figure out which auth method we're trying to call
   async _getAuthMethod() {
     // try getting it from the query string, /.redwood/functions/auth?method=[methodName]
-    let methodName = this.normalizedRequest.query.method as AuthMethodNames
+    let methodName = this.normalizedRequest.query?.method as AuthMethodNames
 
     if (
       !DbAuthHandler.METHODS.includes(methodName) &&