Error when accessing table with undefined param

When using the SQL table() function to define a table with an undefined paramater `table($undefined)`, the database would attempt to access a nil table, and would eventually crash.

util/fncs/batch.go

@@ -17,11 +17,19 @@ package fncs
 import (
 	"context"
 
+	"github.com/abcum/surreal/mem"
 	"github.com/abcum/surreal/sql"
 )
 
 func batch(ctx context.Context, args ...interface{}) (interface{}, error) {
+
 	tb, _ := ensureString(args[0])
 	id, _ := ensureSlice(args[1])
-	return sql.NewBatch(tb, id), nil
+
+	if len(tb) == 0 {
+		return nil, mem.ErrorTBNotFound
+	}
+
+	return sql.NewBatch(tb, id), nil
+
 }

util/fncs/model.go

@@ -17,11 +17,18 @@ package fncs
 import (
 	"context"
 
+	"github.com/abcum/surreal/mem"
 	"github.com/abcum/surreal/sql"
 )
 
 func model(ctx context.Context, args ...interface{}) (interface{}, error) {
+
 	tb, _ := ensureString(args[0])
+
+	if len(tb) == 0 {
+		return nil, mem.ErrorTBNotFound
+	}
+
 	switch len(args) {
 	case 2:
 		if max, ok := ensureFloat(args[1]); ok {
@@ -42,5 +49,7 @@ func model(ctx context.Context, args ...interface{}) (interface{}, error) {
 			}
 		}
 	}
+
 	return nil, nil
+
 }

util/fncs/table.go

@@ -17,10 +17,18 @@ package fncs
 import (
 	"context"
 
+	"github.com/abcum/surreal/mem"
 	"github.com/abcum/surreal/sql"
 )
 
 func table(ctx context.Context, args ...interface{}) (interface{}, error) {
+
 	tb, _ := ensureString(args[0])
-	return sql.NewTable(tb), nil
+
+	if len(tb) == 0 {
+		return nil, mem.ErrorTBNotFound
+	}
+
+	return sql.NewTable(tb), nil
+
 }

util/fncs/thing.go

@@ -17,10 +17,18 @@ package fncs
 import (
 	"context"
 
+	"github.com/abcum/surreal/mem"
 	"github.com/abcum/surreal/sql"
 )
 
 func thing(ctx context.Context, args ...interface{}) (interface{}, error) {
+
 	tb, _ := ensureString(args[0])
-	return sql.NewThing(tb, args[1]), nil
+
+	if len(tb) == 0 {
+		return nil, mem.ErrorTBNotFound
+	}
+
+	return sql.NewThing(tb, args[1]), nil
+
 }