[HAL][ADC] Fix MISRA-C 2012 Rule 15.7 issue

Src/stm32wlxx_hal_adc.c

diff --git a/Src/stm32wlxx_hal_adc.c b/Src/stm32wlxx_hal_adc.c
index 5c843b6..eed1f27 100644
--- a/Src/stm32wlxx_hal_adc.c
+++ b/Src/stm32wlxx_hal_adc.c
@@ -671,6 +671,10 @@
                  | (hadc->ADCGroupRegularSequencerRanks)
                 );
     }
+    else
+    {
+      /* Nothing to do */
+    }
 
     /* Check back that ADC registers have effectively been configured to      */
     /* ensure of no potential problem of ADC core peripheral clocking.        */