<p dir="auto">Am I the first one find it out?</p>
<p dir="auto">v1-beta2 AppBar<br>
If there is an icon button on the left the title, the icon button margin-left is large than margin-top and margin-bottom.</p>
<p dir="auto">I don't know if it is a issue.</p>
<p dir="auto">Since upgrading from material-ui@1.0.0-beta.12 to &gt;=1.0.0-beta.13, my application cannot even boot up, it crashes straight with an error message.</p>


<ul class="contains-task-list">
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> I have searched the <a href="https://github.com/callemall/material-ui/issues">issues</a> of this repository and believe that this is not a duplicate.</li>
</ul>
<h2 dir="auto">Current Behavior</h2>

<p dir="auto">The following error message gets thrown in the form of a "red screen of death":</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="Invariant Violation: Unknown(...): A valid React element (or null) must be returned. You may have returned undefined, an array or some other invalid object.
invariant
webpack:///~/fbjs/lib/invariant.js:42
ReactCompositeComponentWrapper.mountComponent
webpack:///~/react-dom/lib/ReactCompositeComponent.js:192
Object.mountComponent
webpack:///~/react-dom/lib/ReactReconciler.js:43
ReactDOMComponent.mountChildren
webpack:///~/react-dom/lib/ReactMultiChild.js:234
ReactDOMComponent._createInitialChildren
webpack:///~/react-dom/lib/ReactDOMComponent.js:701
ReactDOMComponent.mountComponent
webpack:///~/react-dom/lib/ReactDOMComponent.js:520
Object.mountComponent
webpack:///~/react-dom/lib/ReactReconciler.js:43
ReactCompositeComponentWrapper.performInitialMount
webpack:///~/react-dom/lib/ReactCompositeComponent.js:368
ReactCompositeComponentWrapper.mountComponent
webpack:///~/react-dom/lib/ReactCompositeComponent.js:255
Object.mountComponent
webpack:///~/react-dom/lib/ReactReconciler.js:43"><pre class="notranslate"><code class="notranslate">Invariant Violation: Unknown(...): A valid React element (or null) must be returned. You may have returned undefined, an array or some other invalid object.
invariant
webpack:///~/fbjs/lib/invariant.js:42
ReactCompositeComponentWrapper.mountComponent
webpack:///~/react-dom/lib/ReactCompositeComponent.js:192
Object.mountComponent
webpack:///~/react-dom/lib/ReactReconciler.js:43
ReactDOMComponent.mountChildren
webpack:///~/react-dom/lib/ReactMultiChild.js:234
ReactDOMComponent._createInitialChildren
webpack:///~/react-dom/lib/ReactDOMComponent.js:701
ReactDOMComponent.mountComponent
webpack:///~/react-dom/lib/ReactDOMComponent.js:520
Object.mountComponent
webpack:///~/react-dom/lib/ReactReconciler.js:43
ReactCompositeComponentWrapper.performInitialMount
webpack:///~/react-dom/lib/ReactCompositeComponent.js:368
ReactCompositeComponentWrapper.mountComponent
webpack:///~/react-dom/lib/ReactCompositeComponent.js:255
Object.mountComponent
webpack:///~/react-dom/lib/ReactReconciler.js:43
</code></pre></div>
<h2 dir="auto">Steps to Reproduce (for bugs)</h2>

<ol dir="auto">
<li>Clone <a href="https://github.com/simonyiszk/mvk-web">https://github.com/simonyiszk/mvk-web</a></li>
<li>Upgrade material-ui to the latest version (&gt;=1.0.0-beta.13)</li>
<li>Launch the application using <code class="notranslate">yarn develop</code> or <code class="notranslate">npm run develop</code></li>
<li>Open a web browser at the location shown inside the console</li>
</ol>
<h2 dir="auto">Your Environment</h2>

<table role="table">
<thead>
<tr>
<th>Tech</th>
<th>Version</th>
</tr>
</thead>
<tbody>
<tr>
<td>Material-UI</td>
<td>1.0.0-beta.16</td>
</tr>
<tr>
<td>React</td>
<td>15.6.2</td>
</tr>
<tr>
<td>Browser</td>
<td>Google Chrome 61.0.3163.100 x64</td>
</tr>
<tr>
<td>Gatsby</td>
<td>1.9.55</td>
</tr>
</tbody>
</table>