body is not properly ignored in CASE that has no matching WHEN

the `body` type is ignored because only `branch` is checked,
and so `body` falls into the `throw` for unknown type.

Fix is to add a dynamic check for `body` and ignore it.

instr.h

@@ -525,7 +525,7 @@ public:
         while(it != steps.end())
         {
             bool increased = false;
-            // see if  this is a branch or body
+            // see if this is a branch
             if(dynamic_cast<const branch<CT>*>(*it) || dynamic_cast<const branch<const CT>*>(*it))
             {
                 // branch. Execute it, see if it returns true or false
@@ -558,6 +558,10 @@ public:
                     }
                 }
             }
+            else if(dynamic_cast<const body*>(*it))
+            {
+                // skip body
+            }
             else
             {
                 throw(std::string("invalid type:") + typeid(*it).name());