More sanity checks before calling the help viewer.
More sanity checks before calling the help viewer.

Instead of just going with the assumption that the docview executable exists,
check for it first, before we go any further. Calling TProcess.Execute with
a non-existing executable gives an unwanted error in our applications.

wkitty42/fpGUI,wkitty42/fpGUI,wkitty42/fpGUI,wkitty42/fpGUI,wkitty42/fpGUI,wkitty42/fpGUI