Fix crash when using an inline svg Icon (#5450)

types/mocks.d.ts

@@ -25,7 +25,11 @@ declare module "*.scss" {
 
 // Declare everything what's bundled as webpack's type="asset/resource"
 // Should be mocked for tests support in jestConfig.moduleNameMapper (currently in "/package.json")
-declare module "*.svg";
+declare module "*.svg" {
+  const content: string;
+  export = content;
+}
+
 declare module "*.jpg";
 declare module "*.png";
 declare module "*.eot";