common: utils: Don't output error on empty FRU field

According to the 'Platform Level Data Model (PLDM) for FRU Data
Specification':
"""
All strings shall be preceded by a length variable where a length of
zero indicates that the field is not used.
"""
This means that the length of zero is legit and the parsing code
shouldn't output error on such FRU fields.

Change-Id: I73a72069549fe47071adec50d569122c9a0764d5
Signed-off-by: Konstantin Aladyshev <aladyshev22@gmail.com>
diff --git a/common/utils.cpp b/common/utils.cpp
index 06c256c..82c72d6 100644
--- a/common/utils.cpp
+++ b/common/utils.cpp
@@ -796,7 +796,6 @@
 {
     if (!value || !length)
     {
-        lg2::error("Fru data to string invalid data.");
         return std::nullopt;
     }