BIM : Preserve Spreadsheet structure (#26736)

Signed-off-by: Yash Suthar <yashsuthar983@gmail.com>

src/Mod/BIM/ArchReport.py

@@ -687,7 +687,15 @@ class _ArchReport:
                 f"Report '{getattr(obj, 'Label', '')}': No target spreadsheet found.\n"
             )
             return
-        sp.clearAll()
+        # clear all the content of the spreadsheet
+        used_range = sp.getUsedRange()
+        if used_range:
+            sp.clear(f"{used_range[0]}:{used_range[1]}")
+        else:
+            FreeCAD.Console.PrintError(
+                f"Report '{getattr(obj, 'Label', '')}': Invalid cell address found, clearing spreadsheet.\n"
+            )
+            sp.clearAll()
 
         # Reset the row counter for a new report build.
         self.spreadsheet_current_row = 1

src/Mod/Spreadsheet/App/SheetPyImp.cpp

@@ -1102,6 +1102,9 @@ PyObject* SheetPy::getUsedRange(PyObject* args)
         return nullptr;
     }
     auto usedRange = getSheetPtr()->getCells()->getUsedRange();
+    if (!std::get<0>(usedRange).isValid()) {
+        Py_Return;
+    }
     Py::Tuple pyTuple(2);
     pyTuple[0] = Py::String(std::get<0>(usedRange).toString());
     pyTuple[1] = Py::String(std::get<1>(usedRange).toString());