fix(plugins): empty Lua tables now serialize as [] instead of {} in luaValueToGo

Empty Lua tables from DB queries (e.g. get_events with no results)
are ambiguous — they could be [] or {}. Frontend expects arrays
(with .length), so we default empty tables to [] instead of {}.

internal/core/plugins/api_utils.go

@@ -81,6 +81,16 @@ func luaValueToGo(v lua.LValue) interface{} {
 			}
 			return arr
 		}
+		// Check if table has any keys at all — empty tables are ambiguous.
+		// DB queries return empty tables when no rows match; the frontend
+		// expects a valid array [] (with .length), not {} (where .length is undefined).
+		hasKeys := false
+		val.ForEach(func(k lua.LValue, v lua.LValue) {
+			hasKeys = true
+		})
+		if !hasKeys {
+			return make([]interface{}, 0)
+		}
 		m := make(map[string]interface{})
 		val.ForEach(func(k lua.LValue, v lua.LValue) {
 			m[fmt.Sprintf("%v", k)] = luaValueToGo(v)