Index: driver/catalog.c
===================================================================
--- driver/catalog.c	(revision 1110)
+++ driver/catalog.c	(working copy)
@@ -755,7 +755,8 @@
 
   if (!option_flag(stmt, FLAG_NO_CATALOG))
     db= (is_default_db(stmt->dbc->mysql.db, (char *)szCatalog) ?
-         stmt->dbc->mysql.db : strdup_root(alloc, (char *)szCatalog));
+        stmt->dbc->mysql.db : 
+        (szCatalog ? strdup_root(alloc, (char *)szCatalog) : 0));
 
   if (cbCatalog == SQL_NTS)
     cbCatalog= szCatalog ? strlen((char *)szCatalog) : 0;
Index: test/my_catalog.c
===================================================================
--- test/my_catalog.c	(revision 1110)
+++ test/my_catalog.c	(working copy)
@@ -1269,6 +1269,46 @@
 }
 
 
+/**
+ Bug #30770: AV in myodbc3.dll
+*/
+DECLARE_TEST(t_bug30770)
+{
+  SQLCHAR    buff[512];
+  SQLHENV    henv1;
+  SQLHDBC    hdbc1;
+  SQLHSTMT   hstmt1;
+  SQLCHAR    conn[MAX_NAME_LEN];
+
+
+  ok_sql(hstmt, "DROP TABLE IF EXISTS bug30770");
+  ok_sql(hstmt, "CREATE TABLE bug30770 (a INT)");
+
+  /* Connect with no default daabase */
+  sprintf((char *)conn, "DRIVER=%s;SERVER=%s;" \
+                        "UID=%s;PASSWORD=%s", mydriver, myserver, myuid, mypwd);
+  is(mydrvconnect(&henv1, &hdbc1, &hstmt1, conn) == OK);
+
+  sprintf((char *)buff, "USE %s;", mydb);
+  ok_stmt(hstmt1, SQLExecDirect(hstmt1, buff, SQL_NTS));
+
+  /* Get the info from just one table.  */
+  ok_stmt(hstmt1, SQLColumns(hstmt1, NULL, SQL_NTS, NULL, SQL_NTS, "bug30770",
+                            SQL_NTS, NULL, 0));
+
+  ok_stmt(hstmt1, SQLFetch(hstmt1));
+
+  is_str(my_fetch_str(hstmt1, buff, 3), "bug30770", 9);
+  is_str(my_fetch_str(hstmt1, buff, 4), "a", 1);
+
+  expect_stmt(hstmt1, SQLFetch(hstmt1), SQL_NO_DATA_FOUND);
+  free_basic_handles(&henv1, &hdbc1, &hstmt1);
+
+  ok_sql(hstmt, "DROP TABLE bug30770");
+  return OK;
+}
+
+
 BEGIN_TESTS
   ADD_TEST(my_columns_null)
   ADD_TEST(my_drop_table)
@@ -1295,6 +1335,7 @@
   ADD_TEST(t_bug32989)
   ADD_TEST(t_bug33298)
   ADD_TEST(t_bug12805)
+  ADD_TEST(t_bug30770)
 END_TESTS