[ELF] - Fixed assert fail when symbol table has zero sh_info value.

When sh_info of sumbol table value was set to zero, lld was asserting.

Patch fixes the issue.

Differential revision: https://reviews.llvm.org/D25016

llvm-svn: 283562
diff --git a/lld/ELF/InputFiles.cpp b/lld/ELF/InputFiles.cpp
index dda18aa..d963079 100644
--- a/lld/ELF/InputFiles.cpp
+++ b/lld/ELF/InputFiles.cpp
@@ -81,7 +81,7 @@
   Elf_Sym_Range Syms = ELFObj.symbols(Symtab);
   uint32_t NumSymbols = std::distance(Syms.begin(), Syms.end());
   uint32_t FirstNonLocal = Symtab->sh_info;
-  if (FirstNonLocal > NumSymbols)
+  if (FirstNonLocal == 0 || FirstNonLocal > NumSymbols)
     fatal(getFilename(this) + ": invalid sh_info in symbol table");
 
   if (OnlyGlobals)