Ignore control characters in the text part of Xpe (OSC, Operating System
Control) of the form "ESC]Pn;Pt\a" escape sequences; this matches what
XTerm docs say.
If userTitle is an empty string, set the window title to a blank space
when showWindowTitleOnTitleBar is enabled; basically if the user sets
the title to an empty string, leave it as-is.
BUG: 315581
FIXED-IN: 18.08