disallowSpacesInsideTemplateStringPlaceholders: add additional test

Fixes #2144

Author: markelog

test/specs/rules/disallow-spaces-inside-template-string-placeholders.js

@@ -61,6 +61,10 @@ describe('rules/disallow-spaces-inside-template-string-placeholders', function()
         expect(checker.checkString('`${1}`')).to.have.no.errors();
     });
 
+    it('should not report errors for the backticks without placeholder', function() {
+        expect(checker.checkString('`test`')).to.have.no.errors();
+    });
+
     it('should work with tagged template string', function() {
         expect(checker.checkString('tag`${1}`')).to.have.no.errors();
         expect(checker.checkString('tag`${1 }`')).to.have.one.validation.error