When summoning a falling and entity, or any other entity, riding an item frame with /summon, an internal error occurs. This is the text from console, with one of the bugged commands:

[11:25:39 INFO]: Client> [11:25:39] [Server thread/ERROR]: Couldn't process command: 'summon FallingSand ~ ~10 ~ {TileID:66,Riding:{id:ItemFrame}}'
[11:25:39 INFO]: Client> s: Loading entity NBT
[11:25:39 INFO]: Client> at tu.f(SourceFile:1159) ~[14w19a.jar:?]
[11:25:39 INFO]: Client> at ua.a(SourceFile:158) ~[14w19a.jar:?]
[11:25:39 INFO]: Client> at cm.b(SourceFile:94) ~[14w19a.jar:?]
[11:25:39 INFO]: Client> at z.a(SourceFile:65) [14w19a.jar:?]
[11:25:39 INFO]: Client> at ox.d(SourceFile:606) [14w19a.jar:?]
[11:25:39 INFO]: Client> at ox.a(SourceFile:593) [14w19a.jar:?]
[11:25:39 INFO]: Client> at kb.a(SourceFile:37) [14w19a.jar:?]
[11:25:39 INFO]: Client> at kb.a(SourceFile:9) [14w19a.jar:?]
[11:25:39 INFO]: Client> at fp.a(SourceFile:163) [14w19a.jar:?]
[11:25:39 INFO]: Client> at os.c(SourceFile:134) [14w19a.jar:?]
[11:25:39 INFO]: Client> at net.minecraft.server.MinecraftServer.w(SourceFile:580) [14w19a.jar:?]
[11:25:39 INFO]: Client> at net.minecraft.server.MinecraftServer.v(SourceFile:496) [14w19a.jar:?]
[11:25:39 INFO]: Client> at clf.v(SourceFile:132) [14w19a.jar:?]
[11:25:39 INFO]: Client> at net.minecraft.server.MinecraftServer.run(SourceFile:412) [14w19a.jar:?]
[11:25:39 INFO]: Client> at mz.run(SourceFile:682) [14w19a.jar:?]
[11:25:39 INFO]: Client> Caused by: java.lang.NullPointerException: The validated object is null
[11:25:39 INFO]: Client> at org.apache.commons.lang3.Validate.notNull(Validate.java:222) ~[commons-lang3-3.2.1.jar:3.2.1]
[11:25:39 INFO]: Client> at org.apache.commons.lang3.Validate.notNull(Validate.java:203) ~[commons-lang3-3.2.1.jar:3.2.1]
[11:25:39 INFO]: Client> at ul.a(SourceFile:39) ~[14w19a.jar:?]
[11:25:39 INFO]: Client> at ul.a(SourceFile:212) ~[14w19a.jar:?]
[11:25:39 INFO]: Client> at um.a(SourceFile:169) ~[14w19a.jar:?]
[11:25:39 INFO]: Client> at tu.f(SourceFile:1150) ~[14w19a.jar:?]
[11:25:39 INFO]: Client> ... 14 more
[11:25:39 INFO]: Client> [11:25:39] [Client thread/INFO]: [CHAT] An unknown error occurred while attempting to perform this command

It also occurs with any other sand variant riding an item frame, including sand with a tile id, time set to 0 and 1, etc, as well as any entity riding an item frame or painting. Happens with the entity being ridden in quotations and not in quotations. (Riding:{id:"ItemFrame"}} OR Riding:{id:ItemFrame}})