Deleting unused loop variable causes error

[OregSamSas]

I don't know exactly what caused the bug, but i had experienced similar issues before. It may have been fixed, or reported, so sorry if I missed that.

Prominent informations for mentioning are the followings (by my opinion):

• there was a variable for all sprites named "j"
• after searching for "i" using the addon middle-click-popup (TW version of course), a variable named i showed up in the list (probably because the loop variables)
• after clicking it ((by mistake, but doesn't matter)) it got onto the scripts area (or what is it called?), and also appeared in the global variables list
• by throwing out the "i" variable block to the block palette, the variable got unused but still remained in the list on the left
• after right clicking the lock in the variable list, I clicked "remove variable"
• And just after deleting the newly appeared "i" variable an error occurred showing an attention mark on the application header or whatever (where file, etc. are placed) with saying: "Error: cannot find top block"

Here's a little snapshot from the period of time after the error appeared (probably doesn't say anything new):

[OregSamSas]

I think it was already updated to v 1.8.1