Fix "logMode" exception in Debian11
Caused by Debian11 staying on pyQtGraph 0.11. ndscope expects "logMode" key in the view state dictionary but key is missing before pyQtGraph 0.11.
The use of the key is to make sure the right-click menu matches the view state, which is nice, but not strictly needed. The fix just ignores 'logMode' if missing, and doesn't try to update the menu.