gdi32: GetCharABCWidthsW should not crash on a NULL handle.

dlls/gdi/font.c

@@ -2330,6 +2330,8 @@ BOOL WINAPI GetCharABCWidthsW( HDC hdc, UINT firstChar, UINT lastChar,
     unsigned int i;
     BOOL ret = FALSE;
 
+    if (!dc) return FALSE;
+
     if(dc->gdiFont)
         ret = WineEngGetCharABCWidths( dc->gdiFont, firstChar, lastChar, abc );
     else

dlls/gdi/tests/font.c

@@ -323,6 +323,18 @@ static void test_GdiGetCharDimensions(void)
     DeleteDC(hdc);
 }
 
+static void test_GetCharABCWidthsW(void)
+{
+    BOOL ret;
+    ABC abc[1];
+    typedef BOOL (WINAPI *fnGetCharABCWidthsW)(HDC hdc, UINT first, UINT last, LPABC abc);
+    fnGetCharABCWidthsW GetCharABCWidthsW = (fnGetCharABCWidthsW)GetProcAddress(LoadLibrary("gdi32"), "GetCharABCWidthsW");
+    if (!GetCharABCWidthsW) return;
+
+    ret = GetCharABCWidthsW(NULL, 'a', 'a', abc);
+    ok(!ret, "GetCharABCWidthsW should have returned FALSE\n");
+}
+
 static void test_text_extents(void)
 {
     LOGFONTA lf;
@@ -353,5 +365,6 @@ START_TEST(font)
     test_bitmap_font();
     test_bitmap_font_metrics();
     test_GdiGetCharDimensions();
+    test_GetCharABCWidthsW();
     test_text_extents();
 }