Do not raise an error if an unknown SQL function is found in a CHECK
constraint while parsing the schema of an existing database.

FossilOrigin-Name: cda790280a52d65f98a45bacb9123367b159ac7c
diff --git a/src/resolve.c b/src/resolve.c
index 944fb5c..aeeec88 100644
--- a/src/resolve.c
+++ b/src/resolve.c
@@ -647,7 +647,7 @@
         sqlite3ErrorMsg(pParse, "misuse of aggregate function %.*s()", nId,zId);
         pNC->nErr++;
         is_agg = 0;
-      }else if( no_such_func ){
+      }else if( no_such_func && pParse->db->init.busy==0 ){
         sqlite3ErrorMsg(pParse, "no such function: %.*s", nId, zId);
         pNC->nErr++;
       }else if( wrong_num_args ){