QLocale: add a Q_CHECK_PTR

Avoid complaints from static analyzers that the pointer returned
by malloc might be null.

Change-Id: I3ec3ba03d0b5283dd569200a3040a5fe5990f763
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/text/qlocale_tools.cpp

@@ -362,6 +362,7 @@ double qt_asciiToDouble(const char *num, qsizetype numLen, bool &ok, int &proces
         buffer = reasonableBuffer;
     else
         buffer = static_cast<char *>(malloc(numLen + 1));
+    Q_CHECK_PTR(buffer);
     memcpy(buffer, num, numLen);
     buffer[numLen] = '\0';