symbols: fix use of uninitialized variable

'tmp' is stack allocated so tmp->merge is used uninitialized by
AddModMapEntry(). The value doesn't matter much, but it used to
make some modmap merging decision (which doesn't have many
conflicts usually).

Bug inherited from xkbcomp.

Signed-off-by: Ran Benita <ran234@gmail.com>

src/xkbcomp/symbols.c

@@ -1196,6 +1196,7 @@ HandleModMapDef(SymbolsInfo *info, ModMapDef *def)
 
     ok = true;
     tmp.modifier = ndx;
+    tmp.merge = def->merge;
 
     for (key = def->keys; key != NULL; key = (ExprDef *) key->common.next) {
         xkb_keysym_t sym;