Fixed bug in #toString

Author: Joshua-Dias-Barreto

src/DataFrame/DataFrame.class.st

@@ -2458,7 +2458,9 @@ DataFrame >> toString [
 
 	columnWidths := dataFrame columnNames collect: [ :columnName |
 		                | maxWidth |
-		                maxWidth := columnName size.
+		                columnName isString
+			                ifFalse: [ maxWidth := columnName asString size ]
+			                ifTrue: [ maxWidth := columnName size ].
 		                dataFrame rows do: [ :row |
 			                | value |
 			                value := row at: columnName.
@@ -2467,8 +2469,11 @@ DataFrame >> toString [
 
 	dataFrame columnNames withIndexDo: [ :columnName :index |
 		| paddedColumnName |
-		paddedColumnName := columnName padRightTo: (columnWidths at: index).
-		stringTable nextPutAll: paddedColumnName, '  ' ].
+		paddedColumnName := (columnName isString
+			                     ifFalse: [ columnName asString ]
+			                     ifTrue: [ columnName ]) padRightTo:
+			                    (columnWidths at: index).
+		stringTable nextPutAll: paddedColumnName , '  ' ].
 	stringTable cr.