[SYSDM][DESK] Fix GetDC/ReleaseDC error management (#2707)

## Purpose
[SYSDM]
- When closing System Properties page, log show
(win32ss/user/ntuser/windc.c:749) err: [00060138] GetDC() without ReleaseDC()!
because GetDC() is called (multiple times) without properly calling ReleaseDC() as required in order to release a device context.
- This module also lacks some error management in case null DC are provided (on error).
- LiveCD Userinit, based on SYSDM is affected too.

[DESK]
- Fix missing ReleaseDC related to the spectrum (color depth)

## Proposed changes
- ReleaseDC() added.
- Error management in case of null DC.
- Overall alignement of LiveCD Userinit and SYSDM.

base/system/userinit/livecd.c

@@ -34,6 +34,9 @@ InitLogo(PIMGINFO pImgInfo, HWND hwndDlg)
     COLORREF *pBits;
     INT line, column;
 
+    if (hDC == NULL || hDCLogo == NULL || hDCMask == NULL)
+        goto Cleanup;
+
     ZeroMemory(pImgInfo, sizeof(*pImgInfo));
     ZeroMemory(&bmpi, sizeof(bmpi));
 
@@ -76,7 +79,7 @@ InitLogo(PIMGINFO pImgInfo, HWND hwndDlg)
                 g = GetGValue(Color) * alpha / 255;
                 b = GetBValue(Color) * alpha / 255;
 
-                *pBits++ = b | g << 8 | r << 16 | alpha << 24;
+                *pBits++ = b | (g << 8) | (r << 16) | (alpha << 24);
             }
         }
 
@@ -88,10 +91,11 @@ InitLogo(PIMGINFO pImgInfo, HWND hwndDlg)
     }
 
 Cleanup:
-    DeleteObject(hMask);
-    DeleteObject(hLogo);
-    DeleteDC(hDCMask);
-    DeleteDC(hDCLogo);
+    if (hMask != NULL) DeleteObject(hMask);
+    if (hLogo != NULL) DeleteObject(hLogo);  
+    if (hDCMask != NULL) DeleteDC(hDCMask);
+    if (hDCLogo != NULL) DeleteDC(hDCLogo);    
+    if (hDC != NULL) ReleaseDC(hwndDlg, hDC);
 }