Properly processing non-existing images.

src/Generator/InvoiceGenerator.php

@@ -37,7 +37,7 @@ class InvoiceGenerator
         $new = [];
 
         foreach ($paths as $key => $path) {
-            $new[$key] = file_get_contents(Kernel::getProjectRoot().'/'.$path);
+            $new[$key] = file_exists($path) ? file_get_contents(Kernel::getProjectRoot().'/'.$path) : null;
         }
 
         return $new;

templates/invoice_side.html.twig

@@ -111,10 +111,12 @@
     <tr>
         <td height="50px">{{ 'label_signature'|trans(locale) }}</td>
         <td colspan="2" valign="bottom">
+            {% if images.signature is defined and images.signature is not empty %}
             <img src="{{ images.signature|data_uri(mime='image/png') }}" alt="Signature">
+            {% endif %}
         </td>
     </tr>
-    {% if images.stamp is defined %}
+    {% if images.stamp is defined and images.stamp is not empty %}
     <tr>
         <td colspan="3">
             <img src="{{ images.stamp|data_uri(mime='image/png') }}" alt="Stamp">