extract vendor name from an input string only if one exists. If it doesn't exist output "".  

Input: "Charge Card Transaction - SVB: Uber home from airport from Tahoe trip"
Output: "Uber"
Input: "Charge Card Transaction - SVB: Lyft 1 Ride 09-28"
Output: "Lyft"
Input: "Charge Card Transaction - SVB: Refund"
Output: ""
Input: "Charge Card Transaction - SVB: Room during stay"
Output: