[Stats Revamp] Fix crash after backgrounding app from Stats screen (#20008)

* Avoid NSAttributedString crashing the app when it's being initialized in the background

* Don't rebuild guide view when the app is in the background

Author: staskus

WordPress/Classes/ViewRelated/Stats/Insights/StatsTotalInsightsCell.swift

@@ -269,6 +269,12 @@ class StatsTotalInsightsCell: StatsBaseCell {
 
     // Rebuilds guide view for accessibility only if guide view already exists
     private func rebuildGuideViewIfNeeded() {
+        /// NSAttributedString initialized with HTML on the background  crashes the app
+        /// This method can be called when traitCollectionDidChange which can be triggered when app goes to background
+        guard UIApplication.shared.applicationState != .background else {
+            return
+        }
+
         if guideText != nil,
            let statsSummaryType = statsSummaryType,
            let guideText = StatsTotalInsightsData.makeTotalInsightsGuideText(lastPostInsight: lastPostInsight, statsSummaryType: statsSummaryType) {