Fix crash by returning early from finalCheck() if there is no tree to process.

glslang/Include/revision.h

@@ -2,5 +2,5 @@
 // For the version, it uses the latest git tag followed by the number of commits.
 // For the date, it uses the current date (when then script is run).
 
-#define GLSLANG_REVISION "Overload400-PrecQual.1663"
+#define GLSLANG_REVISION "Overload400-PrecQual.1664"
 #define GLSLANG_DATE "27-Nov-2016"

glslang/MachineIndependent/linkValidate.cpp

@@ -377,6 +377,9 @@ void TIntermediate::mergeErrorCheck(TInfoSink& infoSink, const TIntermSymbol& sy
 //
 void TIntermediate::finalCheck(TInfoSink& infoSink)
 {
+    if (getTreeRoot() == nullptr)
+        return;
+
     if (numEntryPoints < 1) {
         if (source == EShSourceGlsl)
             error(infoSink, "Missing entry point: Each stage requires one entry point");