make MBox::Loader#next return nil once EOF is hit

Previously it was raising a debugging exception. This is a better
interface for writing unit tests against.

diff --git a/lib/sup/mbox/loader.rb b/lib/sup/mbox/loader.rb
index 37d253ebf3cfb66902cd5a4b580cbb41aba1da9c..11b071118c3cf5ad692a02d8fbdd6ad10590090b 100644 (file)
--- a/lib/sup/mbox/loader.rb
+++ b/lib/sup/mbox/loader.rb
@@ -128,7 +128,7 @@ class Loader < Source
         ## 2. at the beginning of an mbox separator (in all other
         ##    cases).
 
-        l = @f.gets or raise "next while at EOF"
+        l = @f.gets or return nil
         if l =~ /^\s*$/ # case 1
           returned_offset = @f.tell
           @f.gets # now we're at a BREAK_RE, so skip past it