Update path determination (#9198)

Author: elenadoty

Crashlytics/Crashlytics/Controllers/FIRCLSMetricKitManager.m

@@ -146,17 +146,21 @@ - (BOOL)processMetricKitPayload:(MXDiagnosticPayload *)diagnosticPayload
   // Also ensure that there is a report from the last run of the app that we can write to.
   NSString *metricKitFatalReportFile;
   NSString *metricKitNonfatalReportFile;
+
   NSString *newestUnsentReportID =
-      [self.existingReportManager.newestUnsentReport.reportID stringByAppendingString:@"/"];
+      self.existingReportManager.newestUnsentReport.reportID
+          ? [self.existingReportManager.newestUnsentReport.reportID stringByAppendingString:@"/"]
+          : nil;
   NSString *currentReportID =
       [_managerData.executionIDModel.executionID stringByAppendingString:@"/"];
-  BOOL fatal = ([diagnosticPayload.crashDiagnostics count] > 0) && (newestUnsentReportID != nil) &&
-               ([self.fileManager
-                   fileExistsAtPath:[activePath stringByAppendingString:newestUnsentReportID]]);
+  BOOL crashlyticsFatalReported =
+      ([diagnosticPayload.crashDiagnostics count] > 0) && (newestUnsentReportID != nil) &&
+      ([self.fileManager
+          fileExistsAtPath:[activePath stringByAppendingString:newestUnsentReportID]]);
 
   // Set the MetricKit fatal path appropriately depending on whether we also captured a Crashlytics
   // fatal event and whether the diagnostic report came from a fatal or nonfatal event.
-  if (fatal) {
+  if (crashlyticsFatalReported) {
     metricKitFatalReportFile = [[activePath stringByAppendingString:newestUnsentReportID]
         stringByAppendingString:FIRCLSMetricKitFatalReportFile];
   } else {