#353 Xena Viewer - no error message opening from CLI

[Terry O'Neill]

When using the command line interface to open a Xena file with the Xena Viewer then if the file is not a valid Xena file an error is not displayed (the loading cursor just stays). This is different from when trying to open from the Xena Viewer GUI by pressing the open button in which case an error message is given if the Xena file is not valid. This is particularly an issue when the windows installer has been used as double clicking on a .xena file will result in a call using the CLI passing the file name as a parameter.