(_mime_parse_mpart_message): One more fix

@@ -334,24 +334,34 @@ _mime_parse_mpart_message (mu_mime_t mime)
 			{
 			  mime->parser_state = MIME_STATE_HEADERS;
 			  mime->flags &= ~MIME_PARSER_HAVE_CR;
-			  mb_length = mime->cur_offset -
-			    mb_offset - mime->line_ndx;
+			  mb_length = mime->cur_offset 
+			                   - mb_offset
+			                   - mime->line_ndx;
 			  if (mime->header_length)
 			    /* this skips the preamble */
+			    {
 			      /* RFC 1521 [Page 30]:
-			       NOTE: The CRLF preceding the encapsulation line
-			       is conceptually attached to the boundary so
-			       that it is possible to have a part that does
-			       not end with a CRLF (line break). Body parts
-			       that must be considered to end with line
+				 NOTE: The CRLF preceding the encapsulation
+				 line is conceptually attached to the boundary
+				 so that it is possible to have a part that
+				 does not end with a CRLF (line break). Body
+				 parts that must be considered to end with line
 				 breaks, therefore, must have two CRLFs
 				 preceding the encapsulation line, the first
 				 of which is part of the preceding body part,
 				 and the second of which is part of the
 				 encapsulation boundary. */
+			      
+			      if (mb_lines)
+				/* to prevent negative values in case of a
+				   malformed message */
+				mb_lines--;
+				  
 			      _mime_append_part (mime, NULL,
 						 mb_offset, mb_length,
-					       mb_lines - 1);
+						 mb_lines);
+			    }
+
 			  if ((&mime->cur_line[mime->line_ndx] - cp2 - 1 >
 			       blength
 			       && !strncasecmp (cp2 + blength + 2, "--", 2))
@@ -361,13 +371,15 @@ _mime_parse_mpart_message (mu_mime_t mime)
 			    {	/* last boundary */
 			      mime->parser_state = MIME_STATE_BEGIN_LINE;
 			      mime->header_length = 0;
-			      break;
 			    }
-			  mime->line_ndx = -1;	/* headers parsing requires empty line */
+			  else
+			    mime->line_ndx = -1; /* headers parsing requires
+						    empty line */
 			  break;
 			}
 		    }
-		  else if (mime->header_length)
+
+		  if (mime->header_length)
 		    mb_lines++;
 
 		  mime->line_ndx = 0;