Repository: mermaid-js/mermaid
File: packages/mermaid/src/diagrams/gantt/ganttRenderer.js (JavaScript)

Code before:
          case 'month':
            bottomXAxis.ticks(timeMonth.every(every));
            break;
        }
      }
    }

    svg
      .append('g')
      .attr('class', 'grid')
      .attr('transform', 'translate(' + theSidePad + ', ' + (h - 50) + ')')
      .call(bottomXAxis)
      .selectAll('text')
      .style('text-anchor', 'middle')
      .attr('fill', '#000')
      .attr('stroke', 'none')
      .attr('font-size', 10)
      .attr('dy', '1em');

    if (diagObj.db.topAxisEnabled() || conf.topAxis) {
      let topXAxis = axisTop(timeScale)
        .tickSize(-h + theTopPad + conf.gridLineStartPadding)
        .tickFormat(timeFormat(axisFormat));

      if (resultTickInterval !== null) {
        const every = parseInt(resultTickInterval[1], 10);
        const interval = resultTickInterval[2];
        const weekday = diagObj.db.getWeekday() || conf.weekday;

        // Get the time domain to check tick count
        const domain = timeScale.domain();
        const minTime = domain[0];
        const maxTime = domain[1];
        const estimatedTicks = getEstimatedTickCount(minTime, maxTime, every, interval);

        // Only apply custom ticks if the count is reasonable
        if (estimatedTicks <= MAX_TICK_COUNT) {
          switch (interval) {
            case 'millisecond':
              topXAxis.ticks(timeMillisecond.every(every));
              break;
            case 'second':
              topXAxis.ticks(timeSecond.every(every));
              break;
            case 'minute':
              topXAxis.ticks(timeMinute.every(every));
              break;
            case 'hour':
              topXAxis.ticks(timeHour.every(every));
              break;
            case 'day':

Review comment (suggestion):
The `parseInt` call should validate that the result is not `NaN`. If `resultTickInterval[1]` contains non-numeric characters, `parseInt` will return `NaN`, which will then be passed to `getEstimatedTickCount` and `dayjs.duration`, potentially causing issues. Consider adding validation:
```javascript
const every = parseInt(resultTickInterval[1], 10);
if (isNaN(every) || every <= 0) {
  log.warn(`Invalid tick interval value: "${resultTickInterval[1]}". Skipping custom tick interval.`);
  // Skip applying custom ticks
} else {
  // ... rest of the logic
}
```

Code after:
            case 'minute':
              bottomXAxis.ticks(timeMinute.every(every));
              break;
            case 'hour':
              bottomXAxis.ticks(timeHour.every(every));
              break;
            case 'day':
              bottomXAxis.ticks(timeDay.every(every));
              break;
            case 'week':
              bottomXAxis.ticks(mapWeekdayToTimeFunction[weekday].every(every));
              break;
            case 'month':
              bottomXAxis.ticks(timeMonth.every(every));
              break;
          }
        }
      }
    }

    svg
      .append('g')
      .attr('class', 'grid')
      .attr('transform', 'translate(' + theSidePad + ', ' + (h - 50) + ')')
      .call(bottomXAxis)
      .selectAll('text')
      .style('text-anchor', 'middle')
      .attr('fill', '#000')
      .attr('stroke', 'none')
      .attr('font-size', 10)
      .attr('dy', '1em');

    if (diagObj.db.topAxisEnabled() || conf.topAxis) {
      let topXAxis = axisTop(timeScale)
        .tickSize(-h + theTopPad + conf.gridLineStartPadding)
        .tickFormat(timeFormat(axisFormat));

      if (resultTickInterval !== null) {
        const every = parseInt(resultTickInterval[1], 10);
        if (isNaN(every) || every <= 0) {
          log.warn(
            `Invalid tick interval value: "${resultTickInterval[1]}". Skipping custom tick interval.`
          );
          // Skip applying custom ticks
        } else {
          const interval = resultTickInterval[2];
          const weekday = diagObj.db.getWeekday() || conf.weekday;

          // Get the time domain to check tick count
          const domain = timeScale.domain();
          const minTime = domain[0];