Fix crash at USB thumb drive insertion

Code that would return for the control endpoint had been removed in the
ST port, which led to a null pointer being used as the this pointer in a
USBDeviceConnected object, which caused a write to a small offset from
address 0, which caused a fault.

Author: Alrik Vidstrom

src/USBHost/USBHost.cpp

@@ -697,11 +697,20 @@ bool USBHost::addEndpoint(USBDeviceConnected * dev, uint8_t intf_nb, USBEndpoint
         default:
             return false;
     }
-
+#else
+    // The code that follows this check shouldn't be executed for a control endpoint
+    if (CONTROL_ENDPOINT == (ep->getType()))
+    {
+        return true;
+    }
 #endif
     ep->dev = dev;
-    dev->addEndpoint(intf_nb, ep);
-
+    // This check might not be necessary when the control endpoint check is added above, but
+    // is included just in case
+    if (nullptr != dev)
+    {
+        dev->addEndpoint(intf_nb, ep);
+    }
     return true;
 }