Regression fix - texture types need to be enabled for non-shader code,

so I'll keep this in.

fsl/fsleyes/gl/textures/texture.py

@@ -143,7 +143,7 @@ class Texture(object):
 
         if textureUnit is not None:
             gl.glActiveTexture(textureUnit)
-
+            gl.glEnable(self.__ttype)
         gl.glBindTexture(self.__ttype, self.__texture)
 
         self.__textureUnit = textureUnit
@@ -154,6 +154,7 @@ class Texture(object):
 
         if self.__textureUnit is not None:
             gl.glActiveTexture(self.__textureUnit)
+            gl.glDisable(self.__ttype)
             
         gl.glBindTexture(self.__ttype, 0)