layers: Fix false positive in pointsize write check

Change-Id: Ia6f0d2b127a37ad75280a02907330bdc809e1e40
diff --git a/layers/shader_validation.cpp b/layers/shader_validation.cpp
index d7bdf08..e676119 100644
--- a/layers/shader_validation.cpp
+++ b/layers/shader_validation.cpp
@@ -915,7 +915,9 @@
         }
     }
 
-    bool found_write = !init_complete && (type == spv::OpMemberDecorate);
+    if (!init_complete && (type == spv::OpMemberDecorate)) return false;
+
+    bool found_write = false;
     std::unordered_set<uint32_t> worklist;
     worklist.insert(entrypoint.word(2));