Fix assertion failure in saveQualifierReferences

Check that the symbol is a class or module before calling asClassOrModuleRef().
This prevents crashes when processing symbols that are not classes or modules
(e.g. fields or methods) but are encountered in contexts where a class or module
reference was assumed.

Amp-Thread-ID: https://ampcode.com/threads/T-3ff237da-1bb4-43d1-abb5-989b228d9f59

Author: jupblb

scip_indexer/SCIPIndexer.cc

@@ -477,7 +477,7 @@ class SCIPState {
                                          ast::ExpressionPtr &constantLitExpr) {
         auto *expr = &constantLitExpr;
         while (auto *constantLit = ast::cast_tree<ast::ConstantLit>(*expr)) {
-            if (constantLit->symbol.exists() && constantLit->symbol.asClassOrModuleRef().exists()) {
+            if (constantLit->symbol.exists() && constantLit->symbol.isClassOrModule() && constantLit->symbol.asClassOrModuleRef().exists()) {
                 core::Context ctx(gs, constantLit->symbol, file);
                 auto status = this->saveReference(ctx, GenericSymbolRef::classOrModule(constantLit->symbol),
                                                   /*overrideType*/ std::nullopt, constantLit->loc, 0);