[CRT] fix null pointer deref in _gmtime64_s CID 515314

svn path=/trunk/; revision=68913

reactos/lib/sdk/crt/time/gmtime.c

@@ -123,7 +123,8 @@ _gmtime64_s(
    struct tm* ptm,
    const __time64_t* ptime)
 {
-    __time64_t time = *ptime;
+    __time64_t time;
+
     if (!ptm)
     {
         MSVCRT_INVALID_PMT("ptm == NULL", ERROR_BAD_COMMAND);
@@ -136,6 +137,8 @@ _gmtime64_s(
         return ERROR_BAD_COMMAND;
     }
 
+    time = *ptime;
+
     _gmtime_worker(ptm, time, 0);
 
     return ERROR_SUCCESS;