Avoid needless second pass on non-glow particles.

indra/newview/lldrawpoolalpha.cpp

@@ -598,6 +598,7 @@ void LLDrawPoolAlpha::renderAlpha(U32 mask, S32 pass)
 				// If this alpha mesh has glow, then draw it a second time to add the destination-alpha (=glow).  Interleaving these state-changing calls could be expensive, but glow must be drawn Z-sorted with alpha.
 				if (current_shader && 
 					draw_glow_for_this_partition &&
+					params.mHasGlow &&	//only do this second pass for batches that actually have glow
 					params.mVertexBuffer->hasDataType(LLVertexBuffer::TYPE_EMISSIVE))
 				{
 					// install glow-accumulating blend mode