[Ada] Remove redundant guard for call to List_Length with a No_List

[Pierre-Marie de Rodat via Gcc-patches]

Code cleanup related to a new detection of uninitialised local scalar
objects; semantics is unaffected.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

        * sem_ch5.adb (Analyze_Block_Statement): Call to List_Length with
        No_List is safe and will return zero.
diff --git a/gcc/ada/sem_ch5.adb b/gcc/ada/sem_ch5.adb
--- a/gcc/ada/sem_ch5.adb
+++ b/gcc/ada/sem_ch5.adb
@@ -1376,11 +1376,7 @@ package body Sem_Ch5 is
          --  Initialize unblocked exit count for statements of begin block
          --  plus one for each exception handler that is present.
 
-         Unblocked_Exit_Count := 1;
-
-         if Present (EH) then
-            Unblocked_Exit_Count := Unblocked_Exit_Count + List_Length (EH);
-         end if;
+         Unblocked_Exit_Count := 1 + List_Length (EH);
 
          --  If a label is present analyze it and mark it as referenced