Forgot one Dutch translation

lang/po/Firmware_nl.po

@@ -261,7 +261,7 @@ msgstr "Kalibratie klaar"
 #: ../../Firmware/mmu2/errors_list.h:203 ../../Firmware/mmu2/errors_list.h:243
 #: ../../Firmware/mmu2/errors_list.h:245
 msgid "Can't move Selector or Idler."
-msgstr ""
+msgstr "Kan selector of riemschijf niet bewegen."
 
 #. MSG_DESC_FILAMENT_ALREADY_LOADED c=20 r=8
 #: ../../Firmware/mmu2/errors_list.h:228 ../../Firmware/mmu2/errors_list.h:266