[BUG] Flush the chainstate after pruning invalid entries.

Fix an edge case where the 'M' key is removed from the blockTree DB but
the chainstate still contains the invalid entries, due to it not being
flushed after the update.

src/init.cpp

@@ -1628,6 +1628,11 @@ bool AppInitMain()
                     if (fZerocoinActive && pblocktree->Read('M', nDummySupply)) {
                         LogPrintf("Pruning zerocoin mints / invalid outs, at height %d\n", chainHeight);
                         pcoinsTip->PruneInvalidEntries();
+                        if (!pcoinsTip->Flush()) {
+                            strLoadError = _("System error while flushing the chainstate after pruning invalid entries. Possible corrupt database.");
+                            break;
+                        }
+                        MoneySupply.Update(pcoinsTip->GetTotalAmount(), chainHeight);
                         pblocktree->Erase('M');
                     }
                 }