Basler backend aborts process when camera is not available

[astraw]

When a Basler camera is in use (by another process), the Basler backend aborts:

/home/astraw/src/motmot/libcamiface/src/cam_iface_basler_pylon.cpp (441): getting the camera: Failed to open/connect to Basler acA640-100gm#0030530F86B0#169.254.4.4:3956. Possibly, the device is controlled by another application.
GX status 0xe1018006 (0x
terminate called after throwing an instance of 'GenICam::RuntimeException'
  what():  Can't read from Register 0x0000000000030224. Access mode is NI (../../genicam-src/GenApi/Register.cpp:189)
Aborted

This is despite (potentially wrong) exception catching in the source code.

[davebenson]

I'd need to see the calling code; the exception appears to be caught ok, but then the application goes on to try and use the camera anyway.

[astraw]

I think I can reproduce this the following way:

1. start an app using libcamiface and a Basler camera with the Pylon backend.
2. start an app using libcamiface, attempting to use a different camera and backend.

In step 2, the following error is thrown:

/home/astraw/src/motmot/libcamiface/src/cam_iface_basler_pylon.cpp (441): getting the camera: Failed to open/connect to Basler acA640-100gc#0030530F8585#169.254.134.133:3956. Possibly, the device is controlled by another application.
GX status 0xe1018006
terminate called after throwing an instance of 'GenICam::RuntimeException'
  what():  Can't read from Register 0x0000000000030224. Access mode is NI (../../genicam-src/GenApi/Register.cpp:189)
Aborted