[otBase] Actually call conv.writeArray()

Huh. Somehow the writeArray() was never wired up. We lose the failing
array index in the exception, but is fine to me.

Lib/fontTools/ttLib/tables/otBase.py

@@ -728,12 +728,11 @@ class BaseTable(object):
 					# conv.repeat is a propagated count
 					writer[conv.repeat].setValue(countValue)
 				values = value
-				for i, value in enumerate(values):
 				try:
-						conv.write(writer, font, table, value, i)
+					conv.writeArray(writer, font, table, values)
 				except Exception as e:
 					name = value.__class__.__name__ if value is not None else conv.name
-						e.args = e.args + (name+'['+str(i)+']',)
+					e.args = e.args + (name+'[]',)
 					raise
 			elif conv.isCount:
 				# Special-case Count values.