hwmontemp: Fix NULL pointer dereference

When createSensors() is called with activateOnly set to false
and a sensor does not have a hwmonFile it is added as nullptr
to sensors array.

This causes interfaceRemoved() to crash as it dereferences
that sensor without first checking if it's null.

Tested: hwmontempsensor no longer crashes when some random
        interface is removed.

Change-Id: I8f63f753cca7341be5a0683e7b446f63ae92f8cb
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
diff --git a/src/HwmonTempMain.cpp b/src/HwmonTempMain.cpp
index 8d41fab..a85d13a 100644
--- a/src/HwmonTempMain.cpp
+++ b/src/HwmonTempMain.cpp
@@ -538,7 +538,7 @@
     auto sensorIt = sensors.begin();
     while (sensorIt != sensors.end())
     {
-        if ((sensorIt->second->configurationPath == path) &&
+        if (sensorIt->second && (sensorIt->second->configurationPath == path) &&
             (std::find(interfaces.begin(), interfaces.end(),
                        sensorIt->second->configInterface) != interfaces.end()))
         {