Blocks are not correctly deleted when a variable is deleted

[anmartan]

There is a problem when the user sets the blocks like this:

And later on they choose to delete the variable (not the variables_set block, but the variable itself), using the delete variable option from the variables_set block (like below):

The variables_set is removed and the rest of the blocks still exist, which would seem like a normal behavior:

But, if the user then tries to move the math block, these exceptions appear:

This block can no longer be erased or connected to other blocks.