Remove check for empty command from pg_conn_t::exec()

It is almost never needed there and is better done outside that function
in the few places where it is needed.

Author: joto

src/middle-pgsql.cpp

@@ -670,7 +670,9 @@ void middle_pgsql_t::start()
             auto const qual_name = qualified_name(table.schema(), table.name());
             m_db_connection.exec(
                 "DROP TABLE IF EXISTS {} CASCADE"_format(qual_name));
-            m_db_connection.exec(table.m_create_table);
+            if (!table.m_create_table.empty()) {
+                m_db_connection.exec(table.m_create_table);
+            }
         }
     }
 }
@@ -873,7 +875,9 @@ middle_pgsql_t::get_query_instance()
 
     // We use a connection per table to enable the use of COPY
     for (auto &table : m_tables) {
-        mid->exec_sql(table.m_prepare_query);
+        if (!table.m_prepare_query.empty()) {
+            mid->exec_sql(table.m_prepare_query);
+        }
     }
 
     return std::shared_ptr<middle_query_t>(mid.release());

src/pgsql.cpp

@@ -66,18 +66,11 @@ void pg_conn_t::set_config(char const *setting, char const *value) const
     query(PGRES_TUPLES_OK, sql);
 }
 
-void pg_conn_t::exec(char const *sql) const
-{
-    if (sql && sql[0] != '\0') {
-        query(PGRES_COMMAND_OK, sql);
-    }
-}
+void pg_conn_t::exec(char const *sql) const { query(PGRES_COMMAND_OK, sql); }
 
 void pg_conn_t::exec(std::string const &sql) const
 {
-    if (!sql.empty()) {
-        query(PGRES_COMMAND_OK, sql.c_str());
-    }
+    query(PGRES_COMMAND_OK, sql.c_str());
 }
 
 void pg_conn_t::copy_start(char const *sql) const