Lets assume this doesn't want to update m_pForcedPrefix->GetText() anyway

The line was like that ever since the code was introduced with
13d20309 "edit control for connection urls," and
Window::GetText() likely never in the past returned a reference to a string.

Change-Id: Ideb5c6a279ac25c2439187a9182f988696818012

dbaccess/source/ui/control/curledit.cxx

@@ -140,7 +140,7 @@ void OConnectionURLEdit::SetText(const OUString& _rStr, const Selection& /*_rNew
 OUString OConnectionURLEdit::GetText() const
 {
     if ( m_pForcedPrefix )
-        return m_pForcedPrefix->GetText() += Edit::GetText();
+        return m_pForcedPrefix->GetText() + Edit::GetText();
     return Edit::GetText();
 }