#5248 bad stack top in nested [dict for]

[Don Porter]

Using a --enable-symbols=all build of either the trunk,
or the 8.6.0 release:

$ cat demo.tcl
apply {{} {
dict for {a b} {c d} {
dict for {e f} {g h} {
return 5
}
}
}}
$ make shell SCRIPT=demo.tcl
...
Bad stack top 4 at pc 104 in TclNRExecuteByteCode (min 0, max 3)
executing dict for {e f} {g h} {
return 5
}
TclNRExecuteByteCode execution failure: bad stack top
make: *** [shell] Abort trap

[Don Porter]

Here's another demo of the issue without the complication
of nesting loops:

apply {{} {
dict for {a b} {c d} {
apply {{} {return -level 2 5}}
}
}}

[Don Porter]

Moving the BEGIN_CATCH before the DICT_FIRST appears
to be an effective fix. Committing to trunk.