Terminal: Fix "nano" titlebar

QTextLayout ignores trailing spaces, and does not draw their
background color. Converting them to Nbsp fixes this.

Change-Id: I19a363bcb4792c613eb9c59f7caaa40fa631b937
Reviewed-by: Cristian Adam <cristian.adam@qt.io>

src/plugins/terminal/terminalwidget.cpp

@@ -390,6 +390,8 @@ void TerminalWidget::copyToClipboard() const
                                         .trimmed());
         }
 
+        selectedText.replace(QChar::Nbsp, QChar::Space);
+
         setClipboardAndSelection(selectedText);
     }
 }