Fix builbots after r364427.

I was using an iterator that was equal to the end of a collection.

llvm-svn: 364447
diff --git a/llvm/lib/DebugInfo/GSYM/Range.cpp b/llvm/lib/DebugInfo/GSYM/Range.cpp
index fdf4c2e..bd10067 100644
--- a/llvm/lib/DebugInfo/GSYM/Range.cpp
+++ b/llvm/lib/DebugInfo/GSYM/Range.cpp
@@ -32,7 +32,7 @@
       // Now check if the previous range intersects with the next range since
       // the previous range was combined. If so, combine them and remove the
       // next range.
-      if (PrevIter->intersect(*Iter))
+      if (Iter != End && PrevIter->intersect(*Iter))
         Ranges.erase(Iter);
       return;
     }