[lldb-dev] assert in symbolfiledwarf.cpp

[Carlo Kok]

In SymbolFileDWARF.cpp:959 there's code like:
     DWARFCompileUnit* dwarf_cu = GetDWARFCompileUnit(sc.comp_unit);
     assert(dwarf_cu);


However in some circumstances it can be that dwarf_cu returns null (if 
the MACH file can't find the compile unit for this source file).

A simple:

     if (!dwarf_cu)
             return false;

Will at least not make it crash(it won't find the symbol, but that's a 
different issue, it shouldn't assert on something like this).