Add a test case for a fixed bug

Previously when "spacing" was set and "allowMultiline" was missing,
it was set to `undefined` and not `true` (as it should).

Author: fatfisz

tests/lib/rules/jsx-curly-spacing.js

@@ -102,6 +102,14 @@ ruleTester.run('jsx-curly-spacing', rule, {
       '} />;'
     ].join('\n'),
     options: [{spaces: 'always', spacing: {}}]
+  }, {
+    code: [
+      '<App foo={',
+      'bar',
+      '} />;'
+    ].join('\n'),
+    options: [{spaces: 'always', spacing: {}}],
+    parserOptions: parserOptions
   }, {
     code: '<App foo={{ bar: true, baz: true }} />;',
     options: [{spaces: 'always', spacing: {objectLiterals: 'never'}}]