chore(website): appease typescript for headlessui v2 upgrade for nullable combobox

Headlessui v2 makes it necessary to handle null input for combobox.

See tailwindlabs/headlessui#3064

Author: corneliusroemer

website/src/components/SearchPage/fields/MutationField.tsx

@@ -168,10 +168,14 @@ export const MutationField: FC<MutationFieldProps> = ({ referenceGenomesSequence
         setOptions(newOptions);
     };
 
-    const handleOptionClick = (option: MutationQuery[] | MutationQuery) => {
+    const handleOptionClick = (option: MutationQuery[] | MutationQuery | null) => {
         if (Array.isArray(option)) {
             option = option[0];
         }
+        // Unclear how to handle null here, necessary since headlessui v2
+        if (!option) {
+            return;
+        }
         const newSelectedOptions = [...selectedOptions, option];
         onChange(serializeMutationQueries(newSelectedOptions));
         setInputValue('');