fixes not concerning graphics

- default is no graphics
- use send_file instead of response (proper mimetype)
- fix issues with parameter blocks

client/jsFiles/SEAWebClientSwiper.js

@@ -171,7 +171,7 @@ function getSlideNames() {
   for (var s=0; s<MAXBLOCK; s++) {
     var sw = swiper[s];
     var name = "";
-    if (sw.activeIndex != defaultSlidePos(s)) {
+    if (sw.activeIndex != defaultSlidePos(s) && sw.slides.length > 0) {
       name = sw.slides[sw.activeIndex].slideType;
     }
     names.push();
@@ -181,4 +181,4 @@ function getSlideNames() {
     names.pop();
   }
   return names;
-}
+}