glTF: Silence uninitialized variable warning

This is a false positive. 'jointNamesIndex' is either set by the loop
or the following conditional is false which also sets it. The undefined value
is never seen by the following code.

code/glTF2Exporter.cpp

@@ -541,7 +541,7 @@ void ExportSkin(Asset& mAsset, const aiMesh* aimesh, Ref<Mesh>& meshRef, Ref<Buf
         Ref<Node> nodeRef = mAsset.nodes.Get(aib->mName.C_Str());
         nodeRef->jointName = nodeRef->name;
 
-        unsigned int jointNamesIndex;
+        unsigned int jointNamesIndex = 0;
         bool addJointToJointNames = true;
         for ( unsigned int idx_joint = 0; idx_joint < skinRef->jointNames.size(); ++idx_joint) {
             if (skinRef->jointNames[idx_joint]->jointName.compare(nodeRef->jointName) == 0) {