fix(ol-interaction-modify): correctly check for source/features

closes #370

Author: d-koppenhagen

Diff for: src/components/interaction/OlInteractionModify.vue

@@ -59,7 +59,7 @@ const {
 } = toRefs(props);
 
 function createModify() {
-  if (!source?.value || !features.value) {
+  if (!(source?.value || !features.value)) {
     console.error(
       `[Vue3-OpenLayers Error] OlInteractionModify: Modify interactions needs either a either a source or features to work.
       Please provide either the props 'source' or 'feature' or use the component with an '<OlSourceVector>' component.`,