Fix segfault caused by accessing non existing key in busmap

Tested:
 - Succesfully boot OpenBMC with error that key does not exist in
   busmap.

Signed-off-by: Wludzik, Jozef <jozef.wludzik@intel.com>
Change-Id: I79736a786f9a88886ee8c54f7c6bf6e32d855769
Signed-off-by: James Feist <james.feist@linux.intel.com>
diff --git a/src/FruDevice.cpp b/src/FruDevice.cpp
index d593c30..0ef0269 100644
--- a/src/FruDevice.cpp
+++ b/src/FruDevice.cpp
@@ -1348,8 +1348,12 @@
                     objServer.remove_interface(busIface.second);
                 }
             }
-            auto& devicemap = busmap[busNum];
-            for (auto& device : *devicemap)
+            auto found = busmap.find(busNum);
+            if (found == busmap.end() || found->second == nullptr)
+            {
+                return;
+            }
+            for (auto& device : *(found->second))
             {
                 AddFruObjectToDbus(device.second, dbusInterfaceMap,
                                    static_cast<uint32_t>(busNum), device.first);