Support parsing empty stack chains.

lib/src/trace.dart

Index: lib/src/trace.dart
diff --git a/lib/src/trace.dart b/lib/src/trace.dart
index 2fce0c7c3d51aa64dc5f1a1eef025d4586b642fd..ce5ec50fe174c00f7916d21b494e547f1154b429 100644
--- a/lib/src/trace.dart
+++ b/lib/src/trace.dart
@@ -188,10 +188,12 @@ class Trace implements StackTrace {
   /// This also parses string representations of [Chain]s. They parse to the
   /// same trace that [Chain.toTrace] would return.
   Trace.parseFriendly(String trace)
-      : this(trace.trim().split("\n")
-          // Filter out asynchronous gaps from [Chain]s.
-          .where((line) => !line.startsWith('====='))
-          .map((line) => new Frame.parseFriendly(line)));
+      : this(trace.isEmpty
+            ? []
+            : trace.trim().split("\n")
+                // Filter out asynchronous gaps from [Chain]s.
+                .where((line) => !line.startsWith('====='))
+                .map((line) => new Frame.parseFriendly(line)));
 
   /// Returns a new [Trace] comprised of [frames].
   Trace(Iterable<Frame> frames)