Thanks, that worked!
But now I have another widget problem. I can't remove a widget I set before. Clicking on save or save&publish lets the animation on the save button rotate endlessly.
So I put the line
Director::set_environment_type('dev');
into mysite/_config.php file and there comes a bunch of messages.....
##############################################
FATAL ERROR: i18n::include_by_class: Class not found
At line 1258 in /var/www/silverstripe/sapphire/core/i18n.php
user_error(i18n::include_by_class: Class not found,512)
line 1258 of i18n.php
i18n::include_by_class()
line 132 of Core.php
_t(TITLE,Title (optional))
line 23 of HtmlContentWidget.php
HtmlContentWidget->getCMSFields()
line 64 of Widget.php
Widget->CMSEditor()
call_user_func_array(Array,Array)
line 404 of ViewableData.php
ViewableData->XML_val(CMSEditor,,1)
line 26 of .cache.var.www.silverstripe.cms.templates.WidgetEditor.ss
include(/var/www/silverstripe/silverstripe-cache/.cache.var.www.silverstripe.cms.templates.WidgetEditor.ss)
line 197 of SSViewer.php
SSViewer->process(HtmlContentWidget)
line 763 of ViewableData.php
ViewableData->renderWith(WidgetEditor)
line 58 of Widget.php
Widget->EditableSegment()
call_user_func_array(Array,Array)
line 404 of ViewableData.php
ViewableData->XML_val(EditableSegment,,1)
line 92 of .cache.var.www.silverstripe.cms.templates.WidgetAreaEditor.ss
include(/var/www/silverstripe/silverstripe-cache/.cache.var.www.silverstripe.cms.templates.WidgetAreaEditor.ss)
line 197 of SSViewer.php
SSViewer->process(WidgetAreaEditor)
line 763 of ViewableData.php
ViewableData->renderWith(WidgetAreaEditor)
line 15 of WidgetAreaEditor.php
WidgetAreaEditor->FieldHolder()
call_user_func_array(Array,Array)
line 404 of ViewableData.php
ViewableData->XML_val(FieldHolder,,1)
line 72 of .cache.var.www.silverstripe.sapphire.templates.TabSetFieldHolder.ss
include(/var/www/silverstripe/silverstripe-cache/.cache.var.www.silverstripe.sapphire.templates.TabSetFieldHolder.ss)
line 197 of SSViewer.php
SSViewer->process(TabSet)
line 763 of ViewableData.php
##############################################
..ok, something is really wrong here I think... do you have a suggestion for me what I can do?