Make sure that we have at least one loc before calculating as suggested by @mdboom

jenshnielsen · tacaswell · commit 01636521b059 · 2016-01-25T19:26:12.000-05:00
diff --git a/lib/matplotlib/ticker.py b/lib/matplotlib/ticker.py
@@ -563,7 +563,7 @@ def _set_offset(self, range):
         locs = np.asarray(locs)
         locs = locs[(vmin <= locs) & (locs <= vmax)]
         ave_loc = np.mean(locs)
-        if ave_loc:  # dont want to take log10(0)
+        if len(locs) and ave_loc:  # dont want to take log10(0)
             ave_oom = math.floor(math.log10(np.mean(np.absolute(locs))))
             range_oom = math.floor(math.log10(range))
 
