Added some improvements for TBigInt shift left operator

UBigInt.pas

@@ -626,8 +626,11 @@ var
 begin
   // Handles shift of zero.
   if A = 0 then
-    Result := TBigInt.Zero
-  else begin
+  begin
+    Result := TBigInt.Zero;
+    Exit;
+  end;
+
   // Determines full digit shifts and bit shifts.
   DivMod(B, CBitsPerDigit, digitShifts, bitShifts);
 
@@ -654,7 +657,7 @@ begin
       Result.FDigits[i] := Result.FDigits[i] or (A.FDigits[j] << bitShifts);
     end;
 
-      if Length(Result.FDigits) > newLength then
+    if lastDigit > 0 then
       Result.FDigits[newLength] := lastDigit;
   end
   else begin
@@ -668,7 +671,6 @@ begin
   end;
 
   Result.FIsNegative := A.IsNegative;
-  end;
 end;
 
 operator shr(const A: TBigInt; const B: Integer): TBigInt;

tests/UBigIntTestCases.pas

@@ -732,7 +732,8 @@ end;
 
 { TBigIntShiftLeftTestCase }
 
-procedure TBigIntShiftLeftTestCase.Test(const AHexValueOperand: string; const AShift: Integer; const AHexValueResult: string);
+procedure TBigIntShiftLeftTestCase.Test(const AHexValueOperand: string; const AShift: Integer; const AHexValueResult:
+  string);
 var
   a, s: TBigInt;
 begin