lib: Fix out-of-bounds array access in i.atcorr/computations.cpp

[ShubhamDesai]

This pull request fixes several instances of out-of-bounds array access in the computations.cpp file within the i.atcorr module. Specifically, it addresses issues where negative indices were being used to access arrays, which could lead to undefined behavior and potential crashes.

Changes Made

• Added a condition to ensure kk is not negative before using it as an array index.
  if (kk < 0) kk = 0;

Issues Resolved

1. Error : Array sixs_trunc.pha[83] accessed at index -1, which is out of bounds.
   Location : imagery/i.atcorr/computations.cpp:116:39
   Details : (double)((log10(sixs_trunc.pha[kk]) - log10(sixs_trunc.pha[k])) /

2. Error : Assuming condition is false
   Location : imagery/i.atcorr/computations.cpp:110:20
   Details : if (rmu[i] > 0.94)

3. Error : Assignment 'kk=i-1', assigned value is -1
   Location : imagery/i.atcorr/computations.cpp:112:16
   Details : kk = i - 1;

4. Error : Negative array index
   Location : imagery/i.atcorr/computations.cpp:116:39
   Details : (double)((log10(sixs_trunc.pha[kk]) - log10(sixs_trunc.pha[k])) /

5. Error : Array rmu[83] accessed at index -1, which is out of bounds.
   Location : imagery/i.atcorr/computations.cpp:117:27
   Details : (acos(rmu[kk]) - acos(rmu[k])));

6. Error : Assuming condition is false
   Location : imagery/i.atcorr/computations.cpp:110:20
   Details : if (rmu[i] > 0.94)

7. Error : Assignment 'kk=i-1', assigned value is -1
   Location : imagery/i.atcorr/computations.cpp:112:16
   Details : kk = i - 1;

8. Error : Negative array index
   Location : imagery/i.atcorr/computations.cpp:117:27
   Details : (acos(rmu[kk]) - acos(rmu[k])));

9. Error : Array sixs_trunc.pha[83] accessed at index -1, which is out of bounds.
   Location : imagery/i.atcorr/computations.cpp:118:46
   Details : double x1 = (double)(log10(sixs_trunc.pha[kk]));

10. Error : Assuming condition is false
    Location : imagery/i.atcorr/computations.cpp:110:20
    Details : if (rmu[i] > 0.94)

11. Error : Assignment 'kk=i-1', assigned value is -1
    Location : imagery/i.atcorr/computations.cpp:112:16
    Details : kk = i - 1;

12. Error : Negative array index
    Location : imagery/i.atcorr/computations.cpp:118:46
    Details : double x1 = (double)(log10(sixs_trunc.pha[kk]));

13. Error : Array rmu[83] accessed at index -1, which is out of bounds.
    Location : imagery/i.atcorr/computations.cpp:119:33
    Details : double x2 = (double)acos(rmu[kk]);

14. Error : Assuming condition is false
    Location : imagery/i.atcorr/computations.cpp:110:20
    Details : if (rmu[i] > 0.94)

15. Error : Assignment 'kk=i-1', assigned value is -1
    Location : imagery/i.atcorr/computations.cpp:112:16
    Details : kk = i - 1;

16. Error : Negative array index
    Location : imagery/i.atcorr/computations.cpp:119:33
    Details : double x2 = (double)acos(rmu[kk]);

[nilason]

@YannChemin Would this minor change to i.atcorr lead to any unintended consequences?