extflat/EFname.c: EFHNBest() add argument ASSERT to convey intention

Adding ASSERT() to arguments to ensure passed arguments are non-NULL
better conveys API intent to both mitigate this false positive
but also allow analysis to inspect caller for correct usage.

SonarCloud
Null pointer passed as 1st argument to string length function
https://sonarcloud.io/project/issues?open=AZJB167jNGfDNup0RjGw&id=dlmiles_magic

extflat/EFname.c

@@ -508,6 +508,9 @@ EFHNBest(hierName1, hierName2)
     HierName *np1, *np2;
     char last1, last2;
 
+    ASSERT(hierName1, "hierName1");
+    ASSERT(hierName2, "hierName2");
+
     for (ncomponents1 = 0, np1 = hierName1; np1; np1 = np1->hn_parent)
 	ncomponents1++;
     for (ncomponents2 = 0, np2 = hierName2; np2; np2 = np2->hn_parent)