Fix several crashes reported through Google Analytics

Fix the following crashes:
* `NullPointerException (@FlightActivity$3:onClick:98) {main}`
* `NullPointerException (@FlightActivity$5:onClick:114) {main}`
* `NullPointerException (@BluetoothConnection:findSerialBluetoothBoard:91) {MavLinkConnection-Connecting Thread}`
* `NullPointerException (@FlightActivity$4:onLongClick:105) {main}`
* `ClassCastException (@SuperSetupMainPanel:onCalibrationData:93) {main}`

Also fixes issue #1022.