Is a victim dies before the assault case goes to court what happens

If--as does not appear to be the case here--the assault led to or contributed to the death (e.g. dying of injuries or complications from the attack), then the charge would typically upgraded to some form of murder.
When the death does not come from the attack, legally, no change is required: the case can go ahead as is. But the state (i.e. the prosecutor's office) will look to the practicalities of the matter. If there was not much evidence other than the victim's testimony, they may choose to drop or dismiss the case, especially if it was simple assault or involved less-severe injuries, because without the victim, they'd have difficulty winning (indeed, winning might be impossible if there was no other evidence beyond victim testimony). Struggling with a likely futile case over a minor assault is something the proscutor may choose to not do. On the other hand, if there is other evidence (e.g. other witness testimony; video surveillance footage; a confession; etc.), then there is no reason why the case cannot proceed without the victim; and especially for more serious assaults, the authorities would be more likely to continue.