A bit more intuitive adding drawing/schedule to the sheet

Now it will detect currently active sheet even if you have sheet's drawing/titleblock/schedule selected.

src/blenderbim/blenderbim/tool/drawing.py

@@ -671,6 +671,11 @@ class Drawing(blenderbim.core.tool.Drawing):
                 new.name = os.path.basename(reference.Location)
                 new.reference_type = reference.Description
 
+    @classmethod
+    def get_active_sheet(cls, context):
+        props = context.scene.DocProperties
+        return next(s for s in props.sheets[: props.active_sheet_index + 1][::-1] if s.is_sheet)
+
     @classmethod
     def import_text_attributes(cls, obj):
         props = obj.BIMTextProperties