fix: Fix no-assigning-return-values 'cannot read property callee of undefined' error (fixes #8)

Author: chrisbreiding

lib/rules/no-assigning-return-values.js

@@ -35,6 +35,9 @@ function isCypressCommandDeclaration(declarator) {
   if (!declarator.init.callee) { return; }
 
   let object = declarator.init.callee.object;
+
+  if (!object)                 { return; }
+
   while (object.callee) {
     object = object.callee.object;
   }

tests/lib/rules/no-assigning-return-values.js

@@ -13,6 +13,7 @@ ruleTester.run('no-assigning-return-values', rule, {
     { code: 'var foo = true;', parserOptions },
     { code: 'let foo = true;', parserOptions },
     { code: 'const foo = true;', parserOptions },
+    { code: 'const foo = bar();', parserOptions },
     { code: 'cy.get("foo");', parserOptions },
     { code: 'cy.contains("foo").click();', parserOptions }
   ],