This patch fixes updating persistent variables when memory cannot be
allocated in an inferior process:
```
> lldb -c test.core
(lldb) expr int $i = 5
(lldb) expr $i = 55
(int) $0 = 55
(lldb) expr $i
(int) $i = 5
```
With this patch, the last command prints:
```
(int) $i = 55
```
The issue was introduced in #145599.
e4c0f30030