Avoid triggering undefined behaviour (std::memset(nullptr, 0, 0)) if an invalid string is passed to DecodeSecret(...)

src/key_io.cpp

@@ -142,7 +142,9 @@ CKey DecodeSecret(const std::string& str)
             key.Set(data.begin() + privkey_prefix.size(), data.begin() + privkey_prefix.size() + 32, compressed);
         }
     }
-    memory_cleanse(data.data(), data.size());
+    if (!data.empty()) {
+        memory_cleanse(data.data(), data.size());
+    }
     return key;
 }
 

test/sanitizer_suppressions/ubsan

@@ -4,7 +4,6 @@ bool:wallet/wallet.cpp
 float-divide-by-zero:policy/fees.cpp
 float-divide-by-zero:validation.cpp
 float-divide-by-zero:wallet/wallet.cpp
-nonnull-attribute:support/cleanse.cpp
 unsigned-integer-overflow:arith_uint256.h
 unsigned-integer-overflow:basic_string.h
 unsigned-integer-overflow:bench/bench.h