Fix eslint crash when using object spread inside prop definition (#295)

* add test for prop default with object spread

* fixes #287:

check for key

lib/rules/require-default-prop.js

@@ -43,13 +43,13 @@ module.exports = {
     }
 
     /**
-     * Checks if the passed prop has a defualt value
+     * Checks if the passed prop has a default value
      * @param {Property} prop - Property AST node for a single prop
      * @return {boolean}
      */
     function propHasDefault (prop) {
       const propDefaultNode = prop.value.properties
-        .find(p => p.key.name === 'default')
+        .find(p => p.key && p.key.name === 'default')
 
       return Boolean(propDefaultNode)
     }

tests/lib/rules/require-default-prop.js

@@ -68,6 +68,34 @@ ruleTester.run('require-default-prop', rule, {
         }
       `,
       parserOptions
+    },
+    {
+      filename: 'test.vue',
+      code: `
+        const x = {
+          type: Object,
+          default() {
+            return {
+              foo: 1,
+              bar: 2
+            }
+          }
+        }
+        export default {
+          props: {
+            a: {
+              ...x,
+              default() {
+                return {
+                  ...x.default(),
+                  baz: 3
+                }
+              }
+            }
+          }
+        }
+      `,
+      parserOptions
     }
   ],