fix: change best fit formula if dataframe is empty (#157)

Co-authored-by: Adi Vaknin <DeepSpace2@users.noreply.github.com>

Author: Exzentttt

styleframe/style_frame.py

@@ -549,8 +549,12 @@ def get_range_of_cells(row_index=None, columns=None):
         if best_fit:
             if not isinstance(best_fit, (list, set, tuple)):
                 best_fit = [best_fit]
-            self.set_column_width_dict({column: (max(self.data_df[column].astype(str).str.len()) + self.A_FACTOR) * self.P_FACTOR
-                                        for column in best_fit})
+            self.set_column_width_dict(
+                {
+                    column: (max(self.data_df[column].astype(str).str.len(), default=0) + self.A_FACTOR) * self.P_FACTOR
+                    for column in best_fit
+                }
+            )
 
         for column in self._columns_width:
             column_letter = self._get_column_as_letter(sheet, column, startcol)