Only try folding constant array indexing if propagated.

The array folding logic generated an error when a constant array didn't
have an array of literal constants.

Change-Id: I48f58936cfa7e19e0f4026fb940654f20d9a9d5e
Reviewed-on: https://swiftshader-review.googlesource.com/15551
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>

src/OpenGL/compiler/ParseHelper.cpp

diff --git a/src/OpenGL/compiler/ParseHelper.cpp b/src/OpenGL/compiler/ParseHelper.cpp
index d057364..00f4829 100644
--- a/src/OpenGL/compiler/ParseHelper.cpp
+++ b/src/OpenGL/compiler/ParseHelper.cpp
@@ -2474,7 +2474,7 @@
 
 	TIntermConstantUnion *indexConstantUnion = indexExpression->getAsConstantUnion();
 
-	if(indexExpression->getQualifier() == EvqConstExpr && indexConstantUnion)
+	if(indexExpression->getQualifier() == EvqConstExpr && indexConstantUnion)   // TODO: Qualifier check redundant?
 	{
 		int index = indexConstantUnion->getIConst(0);
 		if(index < 0)
@@ -2486,7 +2486,7 @@
 			recover();
 			index = 0;
 		}
-		if(baseExpression->getType().getQualifier() == EvqConstExpr)
+		if(baseExpression->getType().getQualifier() == EvqConstExpr && baseExpression->getAsConstantUnion())   // TODO: Qualifier check redundant?
 		{
 			if(baseExpression->isArray())
 			{