fix: edit remove function of singly linked list

[damla]

Add condition to check if the element does not exist in the linked list.

Fixes issue:

• If the user enters an element which does not exist in the linked list, it gives error as shown below:

/Users/test/other/interview/test.js:66
            while (currentNode.element !== element) {
                               ^

TypeError: Cannot read property 'element' of null
    at LinkedList.remove (/Users/damlakoksal/other/interview/test.js:66:32)
    at Object.<anonymous> (/Users/damlakoksal/other/interview/test.js:194:10)
    at Module._compile (node:internal/modules/cjs/loader:1095:14)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1124:10)
    at Module.load (node:internal/modules/cjs/loader:975:32)
    at Function.Module._load (node:internal/modules/cjs/loader:816:12)
    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:79:12)
    at node:internal/main/run_main_module:17:47
    ```

**Changes:**

- Add extra condition to check if the element is in the list or not.

[walidbarakat]

i think it'd not be useful to just log, you need to handle it. you can simple use if-else block to not proceed next if the node isn't exist.

[damla]

Thanks for mentioning! I forgot to add return in there. Will fix it 😊