Fix memory leak for margin view.
Fix memory leak for margin view.

rhaberkorn/scintilla-mirror,rhaberkorn/scintilla-mirror,rhaberkorn/scintilla-mirror,rhaberkorn/scintilla-mirror,rhaberkorn/scintilla-mirror,rhaberkorn/scintilla-mirror,rhaberkorn/scintilla-mirror,rhaberkorn/scintilla-mirror