Problem training nodes without neighbors of type specified by meta-path.

[sunwback]

Hi.

If I have nodes like this

p1 p
p2 p
c1 c
c2 c
w1 w
w2 w

and links

p1 c1
p1 w1
p2 w2
p1 p2
w1 w2
c1 c2

and paths

pcwp 1
pwcp 1

the program will give me a segmentation fault.

I guess that is because I specified meta-path 'pcwp' but p1 does not have a neighbor of type 'c'. When handling a 'pcwp' path starts with p1 it may cause a segmentation fault.

[shangjingbo1226]

Yeah, I think this could be the reason. I will take a look later. If you already have a fix, please send me a pull request. Thanks!