also allow reset.

Next thing to do: Make loading of older jaspfiles actually work.
Just like saving and loading

Author: JorisGoosen

CommonData/dataset.cpp

@@ -67,6 +67,12 @@ void DataSet::showFilter(Filter * f)
 
 void DataSet::showFilter(const std::string &filterName)
 {
+	if(filterName == "")
+	{
+		_shownFilter = nullptr;
+		return;
+	}
+	
 	Filter * found = filter(filterName);;
 
 	try