CComponentsHeader: ensure to have correct font instances after changed font

On possible changed font settings, font objects can be invalid and
we have a crash. With this fix it's possible, that
CNeutrinoApp::setupFont() method clean up header font object itself.


Origin commit data
------------------
Commit: 239496c207
Author: Thilo Graf <dbt@novatux.de>
Date: 2016-12-18 (Sun, 18 Dec 2016)

src/gui/components/cc_frm_header.h

@@ -68,6 +68,8 @@ class CComponentsHeader : public CComponentsForm, public CCTextScreen
 		fb_pixel_t cch_col_text;
 		///property: caption font, see also setCaptionFont()
 		Font* cch_font;
+		///reset font
+		void resetFont();
 
 		///property: internal y-position for all items
 		int cch_items_y;