Fix -Wstring-plus-int warning on clang

src/coins.cpp

@@ -143,7 +143,7 @@ bool CCoinsViewCache::GetNullifier(const uint256 &nullifier, NullifierType type)
             cacheToUse = &cacheSaplingNullifiers;
             break;
         default:
-            throw std::runtime_error("Unknown nullifier type " + type);
+            throw std::runtime_error("Unknown nullifier type");
     }
     CNullifiersMap::iterator it = cacheToUse->find(nullifier);
     if (it != cacheToUse->end())

src/test/coins_tests.cpp

@@ -63,7 +63,7 @@ public:
                 mapToUse = &mapSaplingNullifiers_;
                 break;
             default:
-                throw std::runtime_error("Unknown nullifier type " + type);
+                throw std::runtime_error("Unknown nullifier type");
         }
         std::map<uint256, bool>::const_iterator it = mapToUse->find(nf);
         if (it == mapToUse->end()) {

src/txdb.cpp

@@ -63,7 +63,7 @@ bool CCoinsViewDB::GetNullifier(const uint256 &nf, NullifierType type) const {
             dbChar = DB_SAPLING_NULLIFIER;
             break;
         default:
-            throw runtime_error("Unknown nullifier type " + type);
+            throw runtime_error("Unknown nullifier type");
     }
     return db.Read(make_pair(dbChar, nf), spent);
 }

src/txmempool.cpp

@@ -470,7 +470,7 @@ void CTxMemPool::checkNullifiers(NullifierType type) const
             mapToUse = &mapSaplingNullifiers;
             break;
         default:
-            throw runtime_error("Unknown nullifier type " + type);
+            throw runtime_error("Unknown nullifier type");
     }
     for (const auto& entry : *mapToUse) {
         uint256 hash = entry.second->GetHash();
@@ -590,7 +590,7 @@ bool CTxMemPool::nullifierExists(const uint256& nullifier, NullifierType type) c
         case SAPLING_NULLIFIER:
             return mapSaplingNullifiers.count(nullifier);
         default:
-            throw runtime_error("Unknown nullifier type " + type);
+            throw runtime_error("Unknown nullifier type");
     }
 }