Remove duplicated stack trace from error notifications

pkg/analyzer/lib/src/generated/java_engine.dart

Index: pkg/analyzer/lib/src/generated/java_engine.dart
diff --git a/pkg/analyzer/lib/src/generated/java_engine.dart b/pkg/analyzer/lib/src/generated/java_engine.dart
index 8b10e718bca85283a249356b597f393dad88c88c..affcf8dba1f51d52b0f294db8192e6d4c964acf0 100644
--- a/pkg/analyzer/lib/src/generated/java_engine.dart
+++ b/pkg/analyzer/lib/src/generated/java_engine.dart
@@ -97,7 +97,9 @@ class CaughtException implements Exception {
       }
     } else {
       buffer.writeln(exception.toString());
-      buffer.writeln(stackTrace.toString());
+      if (stackTrace != null) {
+        buffer.writeln(stackTrace.toString());
+      }
     }
   }
 }