Fix hasSynced briefly becoming false

Author: simolus3

packages/powersync_core/lib/src/database/core_version.dart

@@ -60,7 +60,7 @@ extension type const PowerSyncCoreVersion((int, int, int) _tuple) {
   // Note: When updating this, also update the download URL in
   // scripts/init_powersync_core_binary.dart and the version ref in
   // packages/sqlite3_wasm_build/build.sh
-  static const minimum = PowerSyncCoreVersion((0, 3, 11));
+  static const minimum = PowerSyncCoreVersion((0, 3, 12));
 
   /// The first version of the core extensions that this version of the Dart
   /// SDK doesn't support.

packages/powersync_core/lib/src/sync/mutable_sync_status.dart

@@ -88,7 +88,7 @@ final class MutableSyncStatus {
       downloadProgress: downloadProgress?.asSyncDownloadProgress,
       priorityStatusEntries: UnmodifiableListView(priorityStatusEntries),
       lastSyncedAt: lastSyncedAt,
-      hasSynced: lastSyncedAt != null,
+      hasSynced: null, // Stream client is not supposed to set this value.
       uploadError: uploadError,
       downloadError: downloadError,
     );