Remove code that does nothing

It is iterating over all masters in the font, then tries to access the
master by its id and then checks if the master is None, but this can
never happen since we are iterating over already existing masters.

This code is called in a very hot spot, and in a script I’m profiling,
it takes more than 50% of the font build time.

Fixes #646

Lib/glyphsLib/classes.py

@@ -841,7 +841,6 @@ class FontFeaturePrefixesProxy(FontClassesProxy):
 
 class GlyphLayerProxy(Proxy):
     def __getitem__(self, key):
-        self._ensureMasterLayers()
         if isinstance(key, slice):
             return self.values().__getitem__(key)
         elif isinstance(key, int):
@@ -883,16 +882,13 @@ def __len__(self):
         return len(self.values())
 
     def keys(self):
-        self._ensureMasterLayers()
         return self._owner._layers.keys()
 
     def values(self):
-        self._ensureMasterLayers()
         return self._owner._layers.values()
 
     def append(self, layer):
         assert layer is not None
-        self._ensureMasterLayers()
         if not layer.associatedMasterId:
             if self._owner.parent:
                 layer.associatedMasterId = self._owner.parent.masters[0].id
@@ -909,7 +905,6 @@ def remove(self, layer):
         return self._owner.removeLayerForKey_(layer.layerId)
 
     def insert(self, index, layer):
-        self._ensureMasterLayers()
         self.append(layer)
 
     def setter(self, values):
@@ -926,21 +921,6 @@ def setter(self, values):
             self._owner._setupLayer(layer, key)
         self._owner._layers = newLayers
 
-    def _ensureMasterLayers(self):
-        # Ensure existence of master-linked layers (even for iteration, len() etc.)
-        # if accidentally deleted
-        if not self._owner.parent:
-            return
-        for master in self._owner.parent.masters:
-            # if (master.id not in self._owner._layers or
-            #         self._owner._layers[master.id] is None):
-            if self._owner.parent.masters[master.id] is None:
-                newLayer = GSLayer()
-                newLayer.associatedMasterId = master.id
-                newLayer.layerId = master.id
-                self._owner._setupLayer(newLayer, master.id)
-                self.__setitem__(master.id, newLayer)
-
     def plistArray(self):
         return list(self._owner._layers.values())