added backgroundcolor to lower-canvas for svg

less/qfq-bs.css.less

@@ -76,6 +76,10 @@ i.@{spinner_class} {
   }
 }
 
+.lower-canvas {
+  background-color: #fff;
+}
+
 //.form-group.required.control-label:before{
 //  color: red;
 //  content: "*";