fix: NVD3 1.8.1 API compat, null guards, missing brace

- Removed useInteractiveGuideline (not in NVD3 1.8.1 on CDN)
- Added null guards in updateData + updateCharts for navigation-away
- Fixed missing closing brace in updateCharts if block

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

js/pages/serverInfo.js

@@ -50,7 +50,6 @@ function ServerInfoPage(params, container) {
     var perfChart = nv.models.multiChart()
       .margin({ top: 30, right: 75, bottom: 40, left: 75 })
       .color(['darkred', 'yellowgreen'])
-      .useInteractiveGuideline(true)
       .duration(0);
     perfChart.yAxis1.axisLabel('Framerate').tickFormat(d3.format(',d'));
     perfChart.yAxis2.axisLabel('Entities').tickFormat(d3.format(',d'));
@@ -69,7 +68,6 @@ function ServerInfoPage(params, container) {
   nv.addGraph(function () {
     var netChart = nv.models.stackedAreaChart()
       .margin({ top: 0, right: 75, bottom: 40, left: 75 })
-      .useInteractiveGuideline(true)
       .duration(0);
     netChart.yAxis.axisLabel('Network').tickFormat(function (bytes) {
       var fmt = d3.format('.0f');
@@ -87,6 +85,22 @@ function ServerInfoPage(params, container) {
 
     window._netChart = netChart;
   });
+    netChart.yAxis.axisLabel('Network').tickFormat(function (bytes) {
+      var fmt = d3.format('.0f');
+      if (bytes < 1024) return fmt(bytes) + 'B';
+      if (bytes < 1048576) return fmt(bytes / 1024) + 'kB';
+      if (bytes < 1073741824) return fmt(bytes / 1048576) + 'MB';
+      return fmt(bytes / 1073741824) + 'GB';
+    });
+    netChart.xAxis.axisLabel('Time').tickFormat(function (d) { return d3.time.format('%H:%M:%S')(new Date(d)); });
+
+    d3.select('#chart-network').datum([
+      { key: 'IN',  values: [] },
+      { key: 'OUT', values: [] }
+    ]).call(netChart);
+
+    window._netChart = netChart;
+  });
 
   nv.addGraph(function () {
     var playersChart = nv.models.pieChart()
@@ -115,6 +129,10 @@ function ServerInfoPage(params, container) {
   }
 
   function updateData(data) {
+    // Guard: element may be gone if navigated away
+    var fieldsEl = document.getElementById('si-fields');
+    if (!fieldsEl) return;
+
     // Update text fields
     var fieldsHtml = '';
     for (var key in data) {
@@ -124,8 +142,11 @@ function ServerInfoPage(params, container) {
         fieldsHtml += '<div class="col-sm-4"><p><span class="text-white-50">' + key + ':</span> <span>' + val + '</span></p></div>';
       }
     }
-    document.getElementById('si-fields').innerHTML = fieldsHtml;
+    fieldsEl.innerHTML = fieldsHtml;
-    if (data.Hostname) document.getElementById('si-hostname').textContent = data.Hostname;
+    if (data.Hostname) {
+      var hn = document.getElementById('si-hostname');
+      if (hn) hn.textContent = data.Hostname;
+    }
 
     // Collect chart data
     recordedData.push({ ts: Date.now(), data: data });
@@ -136,15 +157,19 @@ function ServerInfoPage(params, container) {
   }
 
   function updateCharts(data) {
+    // Guard: SVG elements may be gone if navigated away
     // Players pie chart
     if (window._playersChart) {
-      d3.select('#chart-players').datum([
+      var pc = d3.select('#chart-players');
+      if (!pc.empty()) {
+        pc.datum([
         { key: 'Queued',  y: data.Queued || 0 },
         { key: 'Joining', y: data.Joining || 0 },
         { key: 'Players', y: data.Players || 0 },
         { key: 'Free',    y: (data.MaxPlayers || 0) - ((data.Joining || 0) + (data.Players || 0)) }
       ]).call(window._playersChart);
       }
+    }
 
     // Performance chart
     var fpsVals = [], entVals = [], netInVals = [], netOutVals = [];