HLSL: Protect against some crashes

hlsl/hlslParseHelper.cpp

@@ -3256,6 +3256,7 @@ void HlslParseContext::decomposeStructBufferMethods(const TSourceLoc& loc, TInte
     if (argAggregate) {
         if (argAggregate->getSequence().empty())
             return;
+		if (argAggregate->getSequence()[0])
 	        bufferObj = argAggregate->getSequence()[0]->getAsTyped();
     } else {
         bufferObj = arguments->getAsSymbolNode();
@@ -3756,6 +3757,7 @@ void HlslParseContext::decomposeSampleMethods(const TSourceLoc& loc, TIntermType
                 return;
         } else {
             if (argAggregate->getSequence().size() == 0 || 
+				argAggregate->getSequence()[0] == nullptr ||
                 argAggregate->getSequence()[0]->getAsTyped()->getBasicType() != EbtSampler)
                 return;
         }
@@ -5294,7 +5296,7 @@ TIntermTyped* HlslParseContext::handleFunctionCall(const TSourceLoc& loc, TFunct
 
             TIntermTyped* arg0 = nullptr;
 
-            if (aggregate && aggregate->getSequence().size() > 0)
+            if (aggregate && aggregate->getSequence().size() > 0 && aggregate->getSequence()[0])
                 arg0 = aggregate->getSequence()[0]->getAsTyped();
             else if (arguments->getAsSymbolNode())
                 arg0 = arguments->getAsSymbolNode();
@@ -5768,7 +5770,7 @@ void HlslParseContext::addStructBuffArguments(const TSourceLoc& loc, TIntermAggr
         std::any_of(aggregate->getSequence().begin(),
                     aggregate->getSequence().end(),
                     [this](const TIntermNode* node) {
-                        return (node->getAsTyped() != nullptr) && hasStructBuffCounter(node->getAsTyped()->getType());
+                        return (node && node->getAsTyped() != nullptr) && hasStructBuffCounter(node->getAsTyped()->getType());
                     });
 
     // Nothing to do, if we didn't find one.