fix connPaired() issue

Author: hathach

boards.txt

@@ -141,7 +141,7 @@ pca10056.upload.wait_for_upload_port=true
 # Build
 pca10056.build.mcu=cortex-m4
 pca10056.build.f_cpu=64000000
-pca10056.build.board=NRF52840_FEATHER
+pca10056.build.board=NRF52840_PCA10056
 pca10056.build.core=nRF5
 pca10056.build.variant=pca10056
 pca10056.build.extra_flags=-DNRF52840_XXAA

libraries/Bluefruit52Lib/src/bluefruit.cpp

@@ -631,7 +631,7 @@ uint16_t AdafruitBluefruit::connHandle(void)
 
 bool AdafruitBluefruit::connPaired(void)
 {
-  return Gap.paired(_conn_hdl);
+  return ( _conn_hdl != BLE_CONN_HANDLE_INVALID ) && Gap.paired(_conn_hdl);
 }
 
 uint16_t AdafruitBluefruit::connInterval(void)