Skip hdKeypath of 'm'

Previously the seed was stored with keypath 'm' so we need to skip this
as well when determining inactive seeds.

src/wallet/walletdb.cpp

@@ -441,10 +441,11 @@ ReadKeyValue(CWallet* pwallet, CDataStream& ssKey, CDataStream& ssValue,
             // Extract some CHDChain info from this metadata if it has any
             if (keyMeta.nVersion >= CKeyMetadata::VERSION_WITH_HDDATA && !keyMeta.hd_seed_id.IsNull() && keyMeta.hdKeypath.size() > 0) {
                 // Get the path from the key origin or from the path string
-                // Not applicable when path is "s" as that indicates a seed
+                // Not applicable when path is "s" or "m" as those indicate a seed
+                // See https://github.com/bitcoin/bitcoin/pull/12924
                 bool internal = false;
                 uint32_t index = 0;
-                if (keyMeta.hdKeypath != "s") {
+                if (keyMeta.hdKeypath != "s" && keyMeta.hdKeypath != "m") {
                     std::vector<uint32_t> path;
                     if (keyMeta.has_key_origin) {
                         // We have a key origin, so pull it from its path vector