fix for u-4306 and u-4163 duplicate tickets for same issue namely import...

Added some checking for no file selected or invalid file selected when importing udt file, also added exception handling and using best match dictionary items from localisation files, too much effort to create new dictionary items ;-}
Generic Exception catches are not good practice. If you are going to try/catch you should know exactly what exception (type's) is going to be handled and why. If it's an unhandled exception, that should bubble up with a full stack trace so it's easy to debug. Large try/catch blocks are also not good practice. If you can remove this try/catch or make it more specific to where an exception can occur (after doing proper error/null checks), I'll pull this in and test.