Check if user provided webURL before trying to access it (#4510)

The check should have already happened in the CLI layer. And we cannot do the check here this function is also shared with export which might not have a filter.

Follow up to https://github.com/alcionai/corso/pull/4496

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src/cli/utils/groups.go

@@ -272,11 +272,11 @@ func FilterGroupsRestoreInfoSelectors(
 ) {
 	var site string
 
+	// It is possible that neither exists as this filter is only
+	// mandatory for restore and not for export.
 	if len(opts.SiteID) > 0 {
 		site = opts.SiteID[0]
-	} else {
+	} else if len(opts.WebURL) > 0 {
-		// using else instead of else if so that it would have a hard
-		// fail in case we somehow miss checking this earlier
 		site = opts.WebURL[0]
 	}