[fix] gva: use once_cell to init db handler without unsafe code

Closes #186 (closed)

lib/modules/blockchain/bc-db-writer/src/lib.rs

@@ -81,6 +81,12 @@ pub struct BcDbRwWithWriter<'w, 'db: 'w> {
     pub w: &'w DbWriter<'w>,
 }
 
+impl<'w, 'db: 'w> std::fmt::Debug for BcDbRwWithWriter<'w, 'db> {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
+        write!(f, "BcDbRwWithWriter {{}}")
+    }
+}
+
 impl<'w, 'db: 'w> durs_bc_db_reader::BcDbWithReader for BcDbRwWithWriter<'w, 'db> {
     type DB = Db;
     type R = DbWriter<'w>;