#5127: Prevent exceptions when trying to access empty columns values …

…on data view items.

This can happen if the tree model filter function is accessing columns on items that are created by the ResourceTreeView base class, which is unaware of those columns.

libs/wxutil/dataview/TreeModel.h

@@ -213,22 +213,25 @@ class TreeModel :
 		// Don't implement operator bool() directly, it can be converted to integer
 		bool getBool() const
 		{
-			return getVariant().GetBool();
+            bool value;
+            return getVariant().Convert(&value) ? value : false;
 		}
 
 		int getInteger() const
 		{
-			return static_cast<int>(getVariant().GetInteger());
+            long value;
+            return getVariant().Convert(&value) ? static_cast<int>(value) : 0;
 		}
 
 		double getDouble() const
 		{
-			return getVariant().GetDouble();
+            double value;
+            return getVariant().Convert(&value) ? value : 0.0;
 		}
 
 		void* getPointer() const
 		{
-			return getVariant().GetVoidPtr();
+			return getVariant().IsNull() ? nullptr : getVariant().GetVoidPtr();
 		}
 
 		operator std::string() const