FIX: Set default t_code even if no t_zoom

Author: effigies

nibabel/nifti1.py

@@ -1692,8 +1692,9 @@ def get_zooms(self, units=None, raise_unknown=False):
         if xyz_code == 'unknown':
             xyz_msg = 'Unknown spatial units'
             xyz_code = 'mm'
-        if t_code == 'unknown' and t_zoom is not None:
-            t_msg = 'Unknown time units'
+        if t_code == 'unknown':
+            if t_zoom is not None:
+                t_msg = 'Unknown time units'
             t_code = 'sec'
         if raise_unknown and (xyz_msg, t_msg) != ('', ''):
             if xyz_msg and t_msg: