fix(events): guard events per user/session against division by zero (Infinity/InfinityB)

[mrmeghana]

Problem

On the Events → Overview tab, when a selected period has events but zero users and zero sessions, the cards render:

• Events Per User: Infinity
• Events Per Session: InfinityB

Reproduced live on release-2503 (app data: totalCount: 120, totalUsersCount: 0, totalSessionCount: 0).

Root cause

Two stacked issues:

1. Wrong division guard in getEventOverview (countly.overview.models.js). The guard returned 0 only when both numerator and denominator were 0:

   ob.totalCount === 0 && ob.totalUsersCount === 0 ? 0 : Number((ob.totalCount / ob.totalUsersCount).toFixed(1))

   So events > 0 with users/sessions = 0 computed events / 0 → Infinity.

2. countlyCommon.getShortNumber doesn't handle non-finite input. Infinity >= 1e9 is true, so (Infinity/1e9).toFixed(1) → "Infinity", then + "B" → "InfinityB". (The per-user card renders the raw value via a number slot, hence plain Infinity; the per-session card goes through getShortNumber, hence InfinityB.)

Fix

• Guard the denominator (!ob.totalUsersCount / !ob.totalSessionCount) for the events-per-user, events-per-session, and their prev* values.
• Add an isFinite guard to getShortNumber so no caller can ever produce InfinityB / NaNK again.

Verification

• Finite values unchanged (12345 → "12.3K", etc.) — no regression.
• Against the real live data object: per-user and per-session now return 0 instead of Infinity; verified visually on the dashboard (cards show 0 / 0).
• ESLint clean on both files.

[Copilot]

Pull request overview

Fixes non-finite (“Infinity” / “InfinityB”) values shown on Events → Overview when the selected period has events but zero users/sessions, by guarding divisions at the model layer and preventing short-number formatting from appending suffixes to non-finite values.

Changes:

• Guard events-per-user/session calculations against zero (or missing) denominators in getEventOverview.
• Add a non-finite input guard to countlyCommon.getShortNumber to avoid producing suffixed strings like InfinityB.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
frontend/express/public/javascripts/countly/countly.common.js	Adds a non-finite guard in getShortNumber so formatting never produces InfinityB.
frontend/express/public/core/events/javascripts/countly.overview.models.js	Fixes division guards for per-user/per-session metrics (current and previous period) to prevent Infinity.