I have a simple solution. A hidden dash.
Trigger 1: Spell is casted, activate trigger 2.
Trigger 2: every 0.01 second of the game, check for unit/doodad offset from caster to teleported point. If something is found, set the teleport point and close trigger 2. Teleport caster.
Note: What this does is it checks from the caster to the teleport point anything that is between its path. If there is something, the checking stop, the caster teleports to that 'something'. If nothing is found however, the caster will simply teleport to the intended point. This is what we call tricking something that's not real.