Remove unnecessary null pointer checks

Fixes #110
diff --git a/source/binary.cpp b/source/binary.cpp
index 4db3226..2c42c92 100644
--- a/source/binary.cpp
+++ b/source/binary.cpp
@@ -815,8 +815,6 @@
 // that a spv_binary_t value is created.
 void spvBinaryDestroy(spv_binary binary) {
   if (!binary) return;
-  if (binary->code) {
-    delete[] binary->code;
-  }
+  delete[] binary->code;
   delete binary;
 }