kernel32: Fix a crash in GetStringTypeW() on NULL input string.

dlls/kernel32/locale.c

@@ -2732,6 +2732,12 @@ BOOL WINAPI GetStringTypeW( DWORD type, LPCWSTR src, INT count, LPWORD chartype
         C2_OTHERNEUTRAL        /* LRE, LRO, RLE, RLO, PDF */
     };
 
+    if (!src)
+    {
+        SetLastError( ERROR_INVALID_PARAMETER );
+        return FALSE;
+    }
+
     if (count == -1) count = strlenW(src) + 1;
     switch(type)
     {

dlls/kernel32/tests/locale.c

@@ -3582,9 +3582,26 @@ static void test_GetStringTypeW(void)
     static const WCHAR space_special[] = {0x09, 0x0d, 0x85};
 
     WORD types[20];
+    BOOL ret;
     WCHAR ch;
     int i;
 
+    /* NULL src */
+    SetLastError(0xdeadbeef);
+    ret = GetStringTypeW(CT_CTYPE1, NULL, 0, NULL);
+    ok(!ret, "got %d\n", ret);
+    ok(GetLastError() == ERROR_INVALID_PARAMETER, "got error %d\n", GetLastError());
+
+    SetLastError(0xdeadbeef);
+    ret = GetStringTypeW(CT_CTYPE1, NULL, 0, types);
+    ok(!ret, "got %d\n", ret);
+    ok(GetLastError() == ERROR_INVALID_PARAMETER, "got error %d\n", GetLastError());
+
+    SetLastError(0xdeadbeef);
+    ret = GetStringTypeW(CT_CTYPE1, NULL, 5, types);
+    ok(!ret, "got %d\n", ret);
+    ok(GetLastError() == ERROR_INVALID_PARAMETER, "got error %d\n", GetLastError());
+
     memset(types,0,sizeof(types));
     GetStringTypeW(CT_CTYPE1, blanks, 5, types);
     for (i = 0; i < 5; i++)