examples/regress_categorical.stat causes crash

[Ben Pfaff]

I get the following on master:

    Program received signal SIGSEGV, Segmentation fault.
    [Switching to Thread -1226672448 (LWP 17195)]
    var_get_type (v=0x1) at ../src/data/variable.c:370
    370     {
    (gdb) bt
    #0  var_get_type (v=0x1) at ../src/data/variable.c:370
    #1  0xb80075aa in pspp_linreg_cache_alloc (depvar=0x9e394e0, 
        indep_vars=0xa0ce380, n=10, p=3) at ../src/math/linreg.c:162
    #2  0xb7ff7a06 in cmd_regression (lexer=0x9f8e500, ds=0x9e31aa0)
        at ../src/language/stats/regression.q:949
    #3  0xb7f898e0 in cmd_parse_in_state (lexer=0x9f8e500, ds=0x9e31aa0, 
        state=CMD_STATE_DATA) at ../src/language/command.c:235
    #4  0xb7f89f08 in cmd_parse (lexer=0x9f8e500, ds=0x9e31aa0)
        at ../src/language/command.c:165
    #5  0x0804a986 in main (argc=6, argv=0xbf870324)
        at ../src/ui/terminal/main.c:149

I don't think that I introduced this problem, but if anyone else
thinks I did I'll try to investigate further.
-- 
"But hey, the fact that I have better taste than anybody else in the
 universe is just something I have to live with. It's not easy being
 me."
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