default layout info including warning

src/storm-dft/storage/dft/DFT.h

@@ -270,6 +270,10 @@ namespace storm {
             }
 
             DFTLayoutInfo const& getElementLayoutInfo(size_t id) const {
+                if(mLayoutInfo.count(id) == 0) {
+                    STORM_LOG_WARN("Layout info for element with id " << id << " not found");
+                    return DFTLayoutInfo();
+                }
                 return mLayoutInfo.at(id);
             }