Revert "#4380 - Refactor (calculatePreviewTop.ts): Update the main fu…

…nction"

This reverts commit 22664e6.

packages/ketcher-macromolecules/src/helpers/calculatePreviewTop.ts

@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  ***************************************************************************/
+import { EditorClassName } from 'ketcher-react';
 import { preview } from '../constants';
 
 export const calculateMonomerPreviewTop = createCalculatePreviewTopFunction(
@@ -31,11 +32,17 @@ function createCalculatePreviewTopFunction(
   height: number,
 ): (target?: DOMRect) => string {
   return function calculatePreviewTop(target?: DOMRect): string {
-    if (!target) {
+    if (!target || !getEditorDOMRect()) {
       return '';
     }
 
     const top = calculateTop(target, height);
     return `${top}px`;
   };
 }
+
+function getEditorDOMRect(): DOMRect | undefined {
+  return document
+    .getElementsByClassName(EditorClassName)[0]
+    ?.getBoundingClientRect();
+}