fixed #689: assert the width and height of rect is big than 0

cocos2dx/cocoa/CCGeometry.cpp

@@ -76,6 +76,9 @@ CCRect::CCRect(void)
 
 CCRect::CCRect(float x, float y, float width, float height)
 {
+	// Only support that, the width and height > 0
+	assert(width > 0 && height > 0);
+
 	origin.x = x;
 	origin.y = y;