[Fix] Fix parsing of the received headers with empty part

src/libmime/mime_headers.c

@@ -1098,8 +1098,14 @@ rspamd_smtp_received_process_part (struct rspamd_task *task,
 			p ++;
 			break;
 		case all_done:
-			*last = p - (const guchar *)data;
-			return npart;
+			if (p > (const guchar *)data) {
+				*last = p - (const guchar *) data;
+				return npart;
+			}
+			else {
+				/* Empty element */
+				return NULL;
+			}
 			break;
 		}
 	}
@@ -1120,9 +1126,11 @@ rspamd_smtp_received_process_part (struct rspamd_task *task,
 		}
 		break;
 	case skip_spaces:
-		*last = p - (const guchar *)data;
+		if (p > c) {
+			*last = p - (const guchar *) data;
 
-		return npart;
+			return npart;
+		}
 	default:
 		break;
 	}

test/lua/unit/received.lua

@@ -121,7 +121,14 @@ context("Received headers parser", function()
       {
         by_hostname = 'example.com',
       },
-    }
+    },
+    {[[from 171-29.br (1-1-1-1.z.com.br [1.1.1.1]) by x.com.br (Postfix) with;ESMTP id 44QShF6xj4z1X for <y.br>; Thu, 21 Mar 2019 23:45:46 -0300 : <g @yi.br>]],
+       {
+         from_hostname = '171-29.br',
+         real_ip = '1.1.1.1',
+         by_hostname = 'x.com.br',
+       }
+    },
   }
 
   local task = ffi.C.rspamd_task_new(nil, nil)