Missed removing one of the assert()'s from the LLVMCreateDisasmCPU() library
API with my 176880 revision.  If a bad Triple is passed in it can also assert.
In this case too it should just return 0 to indicate failure to create the
disassembler.

rdar://13955214


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@182542 91177308-0d34-0410-b5e6-96231b3b80d8