[lldb] Use SmallVector::erase correctly

erase() invalidates the iterator, we must use the returned iterator to
continue iterating.

This does not actually make a difference with the current implementation
of SmallVector (erase will effectively return the same pointer), but it
avoids future confusion.

lldb/source/Utility/Broadcaster.cpp

@@ -202,7 +202,7 @@ bool Broadcaster::BroadcasterImpl::RemoveListener(
     if (!curr_listener_sp) {
       // The weak pointer for this listener didn't resolve, lets' prune it
       // as we go.
-      m_listeners.erase(it);
+      it = m_listeners.erase(it);
       continue;
     }
 
@@ -213,8 +213,8 @@ bool Broadcaster::BroadcasterImpl::RemoveListener(
       if (!it->second)
         m_listeners.erase(it);
       return true;
-    } else
-      it++;
+    }
+    it++;
   }
   return false;
 }