Merge commit from fork

* fix(protocol): Treat string descriptor with zero dsc_length as invalid slice descriptor

Do not use this descriptor in calculation due to possible division by zero;

* fix(protocol): Check data length and dsc length separately

---------

Co-authored-by: Artyom Ivanov <artyom.ivanov@red-soft.ru>

Author: TreeHunter9

src/common/sdl.cpp

@@ -928,8 +928,13 @@ static const UCHAR* sdl_desc(const UCHAR* ptr, DSC* desc)
 	case dtype_text:
 	case dtype_cstring:
 	case dtype_varying:
-		desc->dsc_length += get_word(sdl);
+	{
+		const auto length = get_word(sdl);
+		desc->dsc_length += length;
+		if (length == 0 || desc->dsc_length == 0)
+			return nullptr;
 		break;
+	}
 
 	default:
 		break;