Fix crash in llvm-objdump with -macho -objc-meta-data that was trying dump a non-existent section.
Fix crash in llvm-objdump with -macho -objc-meta-data that was trying dump a non-existent section.

Showed up in running on a large binary with the missing section.  I could create a fake
test case if anyone really wants but the fix is pretty obvious.

rdar://25837034


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@267037 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm