Do an initial syntax check before alteration and after alteration

[werpu]

We still have cases where the code is altered in the wrong way (if some error in the template is present) we need to make a syntax check upfront and prevent code alteration and also run a syntax check after alteration and in an case of an error it must be restored to the old state with an error message.

Since this is not a critical issue I will postpone the fix... In the rare case of something like this happens you can always fall back to the local history to restore your code and then roll the changes in manually.