glsl: Quiet unreachable no-return-from-function warning.
diff --git a/src/glsl/ast_to_hir.cpp b/src/glsl/ast_to_hir.cpp
index 0978100..04b221e 100644
--- a/src/glsl/ast_to_hir.cpp
+++ b/src/glsl/ast_to_hir.cpp
@@ -813,6 +813,8 @@
        */
       return new(mem_ctx) ir_constant(true);
    }
+
+   return NULL;
 }
 
 ir_rvalue *