Handle multipart MIME parsing with no parts

pkg/mime/lib/src/bound_multipart_stream.dart

Index: pkg/mime/lib/src/bound_multipart_stream.dart
diff --git a/pkg/mime/lib/src/bound_multipart_stream.dart b/pkg/mime/lib/src/bound_multipart_stream.dart
index d470034f1ae8d29b80d92a3fe0ab24c15535ff7e..a049b1d11e9859f7d45ff3dc6a6112b6838b74ab 100644
--- a/pkg/mime/lib/src/bound_multipart_stream.dart
+++ b/pkg/mime/lib/src/bound_multipart_stream.dart
@@ -54,8 +54,6 @@ class _MimeMultipart extends MimeMultipart {
 
 class BoundMultipartStream {
    static const int _START = 0;
-   static const int _FIRST_BOUNDARY_ENDING = 111;
-   static const int _FIRST_BOUNDARY_END = 112;
    static const int _BOUNDARY_ENDING = 1;
    static const int _BOUNDARY_END = 2;
    static const int _HEADER_START = 3;
@@ -187,7 +185,7 @@ class BoundMultipartStream {
            if (byte == _boundary[_boundaryIndex]) {
              _boundaryIndex++;
              if (_boundaryIndex == _boundary.length) {
-               _state = _FIRST_BOUNDARY_ENDING;
+               _state = _BOUNDARY_ENDING;
                _boundaryIndex = 0;
              }
            } else {
@@ -197,19 +195,6 @@ class BoundMultipartStream {
            }
            break;
 
-         case _FIRST_BOUNDARY_ENDING:
-           if (byte == CharCode.CR) {
-             _state = _FIRST_BOUNDARY_END;
-           } else {
-             _expectWhitespace(byte);
-           }
-           break;
-
-         case _FIRST_BOUNDARY_END:
-           _expectByteValue(byte, CharCode.LF);
-           _state = _HEADER_START;
-           break;
-
          case _BOUNDARY_ENDING:
            if (byte == CharCode.CR) {
              _state = _BOUNDARY_END;
@@ -222,8 +207,10 @@ class BoundMultipartStream {
 
          case _BOUNDARY_END:
            _expectByteValue(byte, CharCode.LF);
-           _multipartController.close();
-           _multipartController = null;
+           if (_multipartController != null) {
+             _multipartController.close();
+             _multipartController = null;
+           }
            _state = _HEADER_START;
            break;
 
@@ -345,8 +332,10 @@ class BoundMultipartStream {
 
          case _LAST_BOUNDARY_END:
            _expectByteValue(byte, CharCode.LF);
-           _multipartController.close();
-           _multipartController = null;
+           if (_multipartController != null) {
+             _multipartController.close();
+             _multipartController = null;
+           }
            _state = _DONE;
            break;