debugger: handle gracefully tarantool.debug.getsources

Before 2.10 there were not only `getsources` but
whole `tarantool.debug` object also. Handle gracefully
this case using optional chaining syntax in TypeScript

`tarantool?.debug?.getsources`

Author: tsafin

debugger/debugger.ts

@@ -39,7 +39,7 @@ import {Thread, mainThread, mainThreadName, isThread} from "./thread";
 import * as tarantool from "tarantool";
 
 // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
-const luaTarantoolGetSources = tarantool.debug.getsources ?? function(filePath: string) {
+const luaTarantoolGetSources = tarantool?.debug?.getsources ?? function(filePath: string) {
     return null;
 };
 

debugger/tsconfig.json

@@ -21,7 +21,7 @@
         "noHeader": true,
         "luaBundle": "lldebugger.lua",
         "luaBundleEntry": "lldebugger.ts",
-        "luaLibImport": "none",
+        "luaLibImport": "require",
         "noResolvePaths": ["tarantool"]
     }
 }