Fix "ninja check-lldb" crash in IRExecutionUnit.cpp
Fix "ninja check-lldb" crash in IRExecutionUnit.cpp

Summary:
From Adrian McCarthy:

"Running ninja check-lldb now has one crash in a Python process, due to deferencing a null pointer in IRExecutionUnit.cpp:  candidate_sc.symbol is null, which leads to a call with a null this pointer."

Reviewers: zturner, spyffe, amccarth

Subscribers: ted, jingham, lldb-commits

Differential Revision: http://reviews.llvm.org/D17860

git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@263066 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lldb,apple/swift-lldb,llvm-mirror/lldb,llvm-mirror/lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,llvm-mirror/lldb,llvm-mirror/lldb,apple/swift-lldb