Validate declaration before access

The PersistentSymbolTable stores IndexedDeclarations, we should
validate the validity of the Declaration before use - potentially
the declaration isn't valid anymore.

kdevplatform/language/codegen/templateclassgenerator.cpp

@@ -327,7 +327,7 @@ void TemplateClassGenerator::addBaseClass(const QString& base)
     //Search for all super classes
     for (PersistentSymbolTable::Declarations::Iterator it = decl.iterator(); it; ++it) {
         DeclarationPointer declaration = DeclarationPointer(it->declaration());
-        if (declaration->isForwardDeclaration()) {
+        if (!declaration || declaration->isForwardDeclaration()) {
             continue;
         }
 

kdevplatform/template/filters/kdevfilters.cpp

@@ -131,8 +131,7 @@ QVariant ArgumentTypeFilter::doFilter (const QVariant& input, const QVariant& /*
     for(PersistentSymbolTable::Declarations::Iterator it = decl.iterator(); it; ++it)
     {
         auto declaration = it->declaration();
-        if(declaration->isForwardDeclaration())
-        {
+        if (!declaration || declaration->isForwardDeclaration()) {
             continue;
         }