Fix iterator invalidation bug, identified by Coverity.

llvm-svn: 28257
diff --git a/llvm/lib/System/DynamicLibrary.cpp b/llvm/lib/System/DynamicLibrary.cpp
index 0c179fc..056fed0 100644
--- a/llvm/lib/System/DynamicLibrary.cpp
+++ b/llvm/lib/System/DynamicLibrary.cpp
@@ -93,6 +93,7 @@
       if (*I == a_handle) {
         // Note: don't use the swap/pop_back trick here. Order is important.
         OpenedHandles.erase(I);
+        return;
       }
     }
   }