Use proper signed number type

This also suppress the compiler warning:
src/base/bittorrent/torrentimpl.cpp:228:36: warning: comparison of integer expressions of different signedness: ‘int’ and ‘const size_t’ {aka ‘const long unsigned int’} [-Wsign-compare]

src/base/bittorrent/torrentimpl.cpp

@@ -112,7 +112,7 @@ namespace
         QString firstTrackerMessage;
         QString firstErrorMessage;
 #if (LIBTORRENT_VERSION_NUM >= 20000)
-        const size_t numEndpoints = nativeEntry.endpoints.size() * ((hashes.has_v1() && hashes.has_v2()) ? 2 : 1);
+        const auto numEndpoints = static_cast<qsizetype>(nativeEntry.endpoints.size() * ((hashes.has_v1() && hashes.has_v2()) ? 2 : 1));
         trackerEntry.endpoints.reserve(static_cast<decltype(trackerEntry.endpoints)::size_type>(numEndpoints));
         for (const lt::announce_endpoint &endpoint : nativeEntry.endpoints)
         {
@@ -167,8 +167,8 @@ namespace
             }
         }
 #else
-        const int numEndpoints = nativeEntry.endpoints.size();
-        trackerEntry.endpoints.reserve(numEndpoints);
+        const auto numEndpoints = static_cast<qsizetype>(nativeEntry.endpoints.size());
+        trackerEntry.endpoints.reserve(static_cast<decltype(trackerEntry.endpoints)::size_type>(numEndpoints));
         for (const lt::announce_endpoint &endpoint : nativeEntry.endpoints)
         {
             TrackerEntry::EndpointStats trackerEndpoint;