Change CommandObjectTargetSymbolsAdd to require that a target exists;
fixes crash of the form

% lldb
(lldb) target symbols add /tmp/symbols.dSYM
(lldb) Killed: 9

<rdar://problem/13139481> 


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@174267 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/source/Commands/CommandObjectTarget.cpp b/source/Commands/CommandObjectTarget.cpp
index c3306ff..15c05dc 100644
--- a/source/Commands/CommandObjectTarget.cpp
+++ b/source/Commands/CommandObjectTarget.cpp
@@ -4204,7 +4204,7 @@
         CommandObjectParsed (interpreter,
                              "target symbols add",
                              "Add a debug symbol file to one of the target's current modules by specifying a path to a debug symbols file, or using the options to specify a module to download symbols for.",
-                             "target symbols add [<symfile>]"),
+                             "target symbols add [<symfile>]", eFlagRequiresTarget),
         m_option_group (interpreter),
         m_file_option (LLDB_OPT_SET_1, false, "shlib", 's', CommandCompletions::eModuleCompletion, eArgTypeShlibName, "Fullpath or basename for module to find debug symbols for."),
         m_current_frame_option (LLDB_OPT_SET_2, false, "frame", 'F', "Locate the debug symbols the currently selected frame.", false, true)