Automatic blendmode override issues

Example: The blendmode gets set to alphablended when connecting something into the alpha input of the main node, when disconnecting it again the blendmode stays on alphablended(afaik).

This led to some confusion and it took me a while to figure out why i dont have shadows. It should be set back to blendmode off when nothing is connected to the alpha input of the main node.

There are probably more issues related to this as you mentioned in another issue.
Link to the issue: specular-highlights-masked-by-shadows-broke
Overriding the automatic blendmode setting should be possible, so the setting wont get messed up with connecting/disconnecting things into the alpha input afterwards.

Hope the title & description is somewhat clear :)