Add missing "$$=NULL;" in error production in parser.

This fixes a crash from a malformed program bug.

expr.cpp

@@ -1899,8 +1899,8 @@ static void
 lPrintPassedTypes(const char *funName, const std::vector<Expr *> &argExprs) {
     fprintf(stderr, "Passed types:\n\t%s(", funName);
     for (unsigned int i = 0; i < argExprs.size(); ++i) {
-        const Type *t = argExprs[i]->GetType();
-        if (t)
+        const Type *t;
+        if (argExprs[i] != NULL && (t = argExprs[i]->GetType()) != NULL)
             fprintf(stderr, "%s%s", t->GetString().c_str(),
                     (i < argExprs.size()-1) ? ", " : ")\n\n");
         else

parse.yy

@@ -927,6 +927,7 @@ statement
         std::vector<std::string> alternates = MatchStrings(yytext, builtinTokens);
         std::string alts = lGetAlternates(alternates);
         Error(@1, "Syntax error--token \"%s\" unknown.%s", yytext, alts.c_str());
+        $$ = NULL;
     }
     ;
 

stmt.cpp

@@ -239,6 +239,7 @@ DeclStmt::EmitCode(FunctionEmitContext *ctx) const {
             continue;
 
         Symbol *sym = decl->sym;
+        assert(decl->sym != NULL);
         const Type *type = sym->type;
         if (!type)
             continue;
@@ -280,6 +281,7 @@ DeclStmt::EmitCode(FunctionEmitContext *ctx) const {
         }
 
         const llvm::Type *llvmType = type->LLVMType(g->ctx);
+        assert(llvmType != NULL);
 
         if (declaration->declSpecs->storageClass == SC_STATIC) {
             // For static variables, we need a compile-time constant value
@@ -353,11 +355,16 @@ DeclStmt::Optimize() {
 
 Stmt *
 DeclStmt::TypeCheck() {
+    bool encounteredError = false;
     for (unsigned int i = 0; i < declaration->declarators.size(); ++i) {
         Declarator *decl = declaration->declarators[i];
-        if (!decl || !decl->initExpr)
+        if (!decl) {
+            encounteredError = true;
             continue;
+        }
 
+        if (!decl->initExpr)
+            continue;
         decl->initExpr = decl->initExpr->TypeCheck();
         if (!decl->initExpr)
             continue;
@@ -374,7 +381,7 @@ DeclStmt::TypeCheck() {
                 decl->initExpr = decl->initExpr->TypeConv(type, "initializer");
         }
     }
-    return this;
+    return encounteredError ? NULL : this;
 }