Return NULL if the user hasn’t uploaded a picture

template.php

@@ -89,15 +89,20 @@ function bluecheese_election_candidate_ballot_item($variables) {
   $candidate = $variables['candidate'];
   $account = user_load($candidate->uid);
 
-  $picture = theme('image_style', array(
-    'style_name' => 'candidate_thumbnail',
-    'path' => $candidate->field_election_picture[LANGUAGE_NONE][0]['uri'],
-    'alt' => t('@user’s picture', array('@user' => format_username($account))),
-    'attributes' => array(
-      'title' => t('View user picture'),
-      'class' => array('candidate-picture'),
-    ),
-  ));
+  if (!empty($candidate->field_election_picture)) {
+    $picture = theme('image_style', array(
+      'style_name' => 'candidate_thumbnail',
+      'path' => $candidate->field_election_picture[LANGUAGE_NONE][0]['uri'],
+      'alt' => t('@user’s picture', array('@user' => format_username($account))),
+      'attributes' => array(
+        'title' => t('View user picture'),
+        'class' => array('candidate-picture'),
+      ),
+    ));
+  }
+  else {
+    $picture = NULL;
+  }
 
   $full_name = theme('election_candidate_full_name', array('candidate' => $candidate));
   $link = l($picture . $full_name, election_candidate_uri_path($candidate), array('html' => TRUE));