Fix compiler crash on constant arrays in conditions

Code like:

if ("") // blabla
or
if ({1,2}) // bla

causes an "array must be indexed" error and crashes when it tries to
print the variable name of the array - because there is none for a
constant inline array.

This patch throws an "invalid expression" error instead.

compiler/sc1.cpp

@@ -5926,8 +5926,10 @@ static int test(int label,int parens,int invert)
   if (endtok!=0)
     needtoken(endtok);
   if (ident==iARRAY || ident==iREFARRAY) {
-    const char *ptr=sym->name;
-    error(33,ptr);              /* array must be indexed */
+    if (sym)
+      error(33, (const char *)sym->name); /* array must be indexed */
+    else
+      error(29);                /* invalid expression */
   } /* if */
   if (ident==iCONSTEXPR) {      /* constant expression */
     int testtype=0;