Handle out-of-bound exception for toHex API

toHex API throws out-of-bound error if provided input length/size is
greater than 15.

This commit adds code to handle the above error case.

Change-Id: Icd4eb2e3655389e194f621fff9d6df251b851c0a
Signed-off-by: Rekha Aparna <vrekhaaparna@ibm.com>
diff --git a/vpd-manager/include/utility/vpd_specific_utility.hpp b/vpd-manager/include/utility/vpd_specific_utility.hpp
index 4a821d2..fa8c3fc 100644
--- a/vpd-manager/include/utility/vpd_specific_utility.hpp
+++ b/vpd-manager/include/utility/vpd_specific_utility.hpp
@@ -193,13 +193,46 @@
         {
             l_result.clear();
             size_t l_firstByte = i_keyword[0];
-            l_result += commonUtility::toHex(l_firstByte >> 4);
-            l_result += commonUtility::toHex(l_firstByte & 0x0f);
+
+            auto l_hexValue = commonUtility::toHex(l_firstByte >> 4);
+
+            if (!l_hexValue)
+            {
+                throw std::runtime_error("Out of bound error");
+            }
+
+            l_result += l_hexValue;
+
+            l_hexValue = commonUtility::toHex(l_firstByte & 0x0f);
+
+            if (!l_hexValue)
+            {
+                throw std::runtime_error("Out of bound error");
+            }
+
+            l_result += l_hexValue;
+
             for (size_t i = 1; i < i_keyword.size(); ++i)
             {
                 l_result += ":";
-                l_result += commonUtility::toHex(i_keyword[i] >> 4);
-                l_result += commonUtility::toHex(i_keyword[i] & 0x0f);
+
+                l_hexValue = commonUtility::toHex(i_keyword[i] >> 4);
+
+                if (!l_hexValue)
+                {
+                    throw std::runtime_error("Out of bound error");
+                }
+
+                l_result += l_hexValue;
+
+                l_hexValue = commonUtility::toHex(i_keyword[i] & 0x0f);
+
+                if (!l_hexValue)
+                {
+                    throw std::runtime_error("Out of bound error");
+                }
+
+                l_result += l_hexValue;
             }
         }
         else if (i_encoding == "DATE")