cc_draw: try to fix logic inside setFrameThickness()

Signed values had the same effects like unsigned values. Therefore
frames were enabled with default control value -1 too.

src/gui/components/cc_draw.cpp

@@ -237,7 +237,7 @@ void CCDraw::setFrameThickness(const int& thickness)
 
 	//ensure enabled frame if frame width > 0
 	cc_enable_frame = false;
-	if (fr_thickness)
+	if (fr_thickness > 0)
 		cc_enable_frame = true;
 }