Adds a check for assigned target not being null when creating an asset

[Godmartinz]

This adds a $target check when assigning during creating an asset. It will now redirect back
Returns a message of The assigned user could not be found.

also a similar error message for assigned asset and locations

[what-the-diff]

PR Summary

• Refined Location Determination Logic in 'store' Method
  In the 'store' method of 'AssetsController', we enhanced its logic to detect the 'location'. Now, if the 'location_id' is not set for both 'User' and 'Asset' targets, the system will intelligently revert to use 'rtd_location_id' instead. This will help ensure the location is always identified accurately.

[snipe]

Are we sure that's the behavior we want? Also, I don't think that directly addresses the rollbar, which was triggered on the line before. It's the target that was null,

[Godmartinz]

whoops i misread the rollbar.. working on it!

[snipe]

Alright quickdraw :D

Man, really dating myself here.

[snipe]

I feel like the bigger question here is why would that target be null?