Fix edge case in analytical integral of exponential TF1

[swetank18]

Motivation:
The analytical integral for exponential TF1 functions does not handle the
p1 -> 0 limit and may result in division by zero or numerical instability.

Changes:

• Handle the p1 == 0 case using the correct analytical limit
• Preserve existing behavior for non-zero slopes

Impact:

• Improves numerical robustness of TF1 analytical integrals
• No API changes

[hageboeck]

Hello, thanks for the contribution!

The change looks reasonable. Could you run something like git clang-format HEAD~ on the commit? Otherwise, the CI will fail on the formatting checks.

[swetank18]

Hello, thanks for the contribution!

The change looks reasonable. Could you run something like git clang-format HEAD~ on the commit? Otherwise, the CI will fail on the formatting checks.

Thank you for the review.
I’ve applied git clang-format to the commit and pushed the updated changes.

[github-actions]

Test Results

    22 files      22 suites   3d 13h 19m 37s ⏱️
 3 774 tests  3 772 ✅ 0 💤 2 ❌
75 056 runs  75 054 ✅ 0 💤 2 ❌

For more details on these failures, see this check.

Results for commit 319674f.

[hageboeck]

The work here will be included in #21060