Use of NULL pointer in qmljstypedescriptionreader.cpp

Look at lines 499ff in src/libs/qmljs/qmljstypedescriptionreader.cpp:

    if (!ast || !ast->statement) {
        addError(ast->colonToken, tr("Expected numeric literal after colon."));
        return invalidVersion;
    }

I expect a crash there if ast is NULL.

Please double-check this and fix it if needed.

Found by Clang Static Analyzer.