fix: Prevent segmentation fault at Simple generic Stack

[Artursrossi]

Description of Change

• Prevent segmentation fault error at stack.c grow function
  • After malloc, there is an iteration without any check if malloc returned null

References

Checklist

• Added description of change
• PR title follows semantic commit guidelines
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Notes: Used realloc instead of malloc

[vil02]

In principle this is a change in a very good direction: standard functions are always better than manual work.

[Artursrossi]

I used assert() function just to maintain the file code standard. In other functions like initStack(), push() and pop(), the original author chose to use assert().