Fix GH-14637: memory leak after failed heap allocation due to mem limit.

[devnexen]

No description provided.

[nielsdos]

This change is right, but doesn't solve the fundamental problem, e.g. slightly modifying the script makes you hit the problem again in a different way.
GH-14637 is actually a duplicate of #14044, and I think it should be closed as such.
This PR may be merged however (if you clean up the comments) because it's a nice optimization on its own.

[devnexen]

oh I am far to understand the whole extension :)