Fixed logic that was passing NULL to a std::string parameter and
crashing dumpstate.

BUG: 8420215
Change-Id: If2f3ebad559683b5b6a8c2209de93ac3bec4fb1e
diff --git a/cmds/dumpstate/dumpstate.h b/cmds/dumpstate/dumpstate.h
index 26e16d0..9623e36 100644
--- a/cmds/dumpstate/dumpstate.h
+++ b/cmds/dumpstate/dumpstate.h
@@ -140,7 +140,7 @@
 void dumpstate_board();
 
 /* Takes a screenshot and save it to the given file */
-void take_screenshot(std::string path);
+void take_screenshot(const std::string& path);
 
 #ifdef __cplusplus
 }