[MRG] fix for annotations when plotting (#3517)

* FIX for annot when meas_date has one element

* TST plt.close('all') to free memory

mne/annotations.py

@@ -119,7 +119,9 @@ def _onset_to_seconds(raw, onset):
     if meas_date is None:
         meas_date = 0
     elif not np.isscalar(meas_date):
-        meas_date = meas_date[0] + meas_date[1] / 1000000.
+        if len(meas_date) > 1:
+            meas_date[1] /= 1e6
+        meas_date = meas_date.sum()
     if raw.annotations.orig_time is None:
         orig_time = meas_date
     else:

mne/viz/tests/test_raw.py

@@ -2,6 +2,7 @@
 #
 # License: Simplified BSD
 
+import numpy as np
 import os.path as op
 import warnings
 
@@ -121,6 +122,13 @@ def test_plot_raw():
                             kind='release')
 
             plt.close('all')
+        # test if meas_date has only one element
+        raw.info['meas_date'] = np.array([raw.info['meas_date'][0]],
+                                         dtype=np.int32)
+        raw.annotations = Annotations([1 + raw.first_samp / raw.info['sfreq']],
+                                      [5], ['bad'])
+        raw.plot()
+        plt.close('all')
 
 
 @requires_version('scipy', '0.10')