When Ctrl+F is hit, search textfield is activated but its contents are unchanged and not selected so one has to write down the text to search. This patch is fixing this behaviour to match regular editor behaviour:

• selected text is put into the search textfield
• content of search textfield is selected
• if there is no selected text in editor, search textfield is activated and its existing content is selected

• select text in lister and press Ctrl+F and press F3 several times (search field should be filled with selected text)
• select different text and press Ctrl+F and press F3 several times (search field should be filled with selected text)
• unselect any text in lister and press Ctrl+F (search field content should stay untouched, it should only get selected)