do not error if typings for external library is empty .d.ts file

src/compiler/program.ts

@@ -1490,7 +1490,7 @@ namespace ts {
                         if (importedFile && resolution.isExternalLibraryImport) {
                             // Since currently irrespective of allowJs, we only look for supportedTypeScript extension external module files,
                             // this check is ok. Otherwise this would be never true for javascript file
-                            if (!isExternalModule(importedFile)) {
+                            if (!isExternalModule(importedFile) && importedFile.statements.length) {
                                 const start = getTokenPosOfNode(file.imports[i], file);
                                 fileProcessingDiagnostics.add(createFileDiagnostic(file, start, file.imports[i].end - start, Diagnostics.Exported_external_package_typings_file_0_is_not_a_module_Please_contact_the_package_author_to_update_the_package_definition, importedFile.fileName));
                             }

tests/baselines/reference/noErrorOnEmptyDts.js

@@ -0,0 +1,13 @@
+//// [tests/cases/compiler/noErrorOnEmptyDts.ts] ////
+
+//// [test.d.ts]
+
+
+// comment
+
+//// [main.ts]
+import "test"
+
+//// [main.js]
+"use strict";
+require("test");

tests/baselines/reference/noErrorOnEmptyDts.symbols

@@ -0,0 +1,8 @@
+=== c:/node_modules/test.d.ts ===
+
+No type information for this code.
+No type information for this code.// comment
+No type information for this code.
+No type information for this code.=== c:/app/main.ts ===
+import "test"
+No type information for this code.

tests/baselines/reference/noErrorOnEmptyDts.types

@@ -0,0 +1,8 @@
+=== c:/node_modules/test.d.ts ===
+
+No type information for this code.
+No type information for this code.// comment
+No type information for this code.
+No type information for this code.=== c:/app/main.ts ===
+import "test"
+No type information for this code.

tests/cases/compiler/noErrorOnEmptyDts.ts

@@ -0,0 +1,8 @@
+// @module: commonjs
+
+// @filename: c:/node_modules/test.d.ts
+
+// comment
+
+// @filename: c:/app/main.ts
+import "test"