--- a/toolkit/components/crashes/CrashService.js
+++ b/toolkit/components/crashes/CrashService.js
@@ -120,17 +120,19 @@ function processExtraFile(extraPath) {
       let extraData = await OS.File.read(extraPath);
       let keyValuePairs = parseKeyValuePairs(decoder.decode(extraData));
 
       // When reading from an .extra file literal '\\n' sequences are
       // automatically unescaped to two backslashes plus a newline, so we need
       // to re-escape them into '\\n' again so that the fields holding JSON
       // strings are valid.
       [ "TelemetryEnvironment", "StackTraces" ].forEach(field => {
-        keyValuePairs[field] = keyValuePairs[field].replace(/\n/g, "n");
+        if (field in keyValuePairs) {
+          keyValuePairs[field] = keyValuePairs[field].replace(/\n/g, "n");
+        }
       });
 
       return keyValuePairs;
     } catch (e) {
       Cu.reportError(e);
       return {};
     }
   })();
@@ -220,17 +222,22 @@ CrashService.prototype = Object.freeze({
     switch (topic) {
       case "profile-after-change":
         // Side-effect is the singleton is instantiated.
         Services.crashmanager;
         break;
       case "quit-application":
         gQuitting = true;
         gRunningProcesses.forEach((process) => {
-          process.kill();
+          try {
+            process.kill();
+          } catch (e) {
+            // If the process has already quit then kill() fails, but since
+            // this failure is benign it is safe to silently ignore it.
+          }
           Services.obs.notifyObservers(null, "test-minidump-analyzer-killed");
         });
         break;
     }
   },
 });
 
 this.NSGetFactory = XPCOMUtils.generateNSGetFactory([CrashService]);