Terminate with error if missing timeseries file path #2440
Description
When a UZT input file is using timeseries but missing the 'TS6 FILEIN ' line the program can crash. Maybe this also affects other packages, not sure.
Discovered by @Manangka in modflowpy/flopy#2280 (comment)
When timeseries are defined a hashtable is created storing the timeseries data. In this case that wasn't happening because of the missing line. There is a dependency on the timeseries however in the perioddata of the uzt package. When it tries to retrieve the value of PFOS it results in a crash. We should probably create an issue to prevent a hard crash. A simple null check could be sufficient