Solve the programming task below in a Python markdown code block.
The local transport authority is organizing an online picture contest.
Participants must take pictures of transport means in an original way, and then post the picture on Instagram using a specific ```hashtag```.

The local transport authority needs your help. They want you to take out the ```hashtag``` from the posted message. Your task is to implement the function

```python
def omit_hashtag(message, hashtag):
```

## Examples 

```
* ("Sunny day! #lta #vvv", "#lta") -> "Sunny day!  #vvv" (notice the double space)
* ("#lta #picture_contest", "#lta") -> " #picture_contest"
```

## Notes

* When multiple occurences of the hashtag are found, delete only the first one.

* In C, you should modify the ```message```, as the function returns a void type. In Python, you should return the answer.

* There can be erroneous messages where the hashtag isn't present. The message should in this case stay untouched.

* The hashtag only consists of alphanumeric characters.
Also feel free to reuse/extend the following starter code:
```python
def omit_hashtag(message, hashtag):
```