refactor: suppress clang false positives (#23154)

src/nvim/eval/userfunc.c

@@ -536,6 +536,7 @@ int get_func_tv(const char *name, int len, typval_T *rettv, char **arg, evalarg_
                                 : funcexe->fe_partial->pt_argc),
                                argvars, &argcount);
 
+  assert(ret == OK || ret == FAIL);  // suppress clang false positive
   if (ret == OK) {
     int i = 0;
 

src/nvim/runtime.c

@@ -253,6 +253,7 @@ void ex_runtime(exarg_T *eap)
   int flags = eap->forceit ? DIP_ALL : 0;
   char *p = skiptowhite(arg);
   flags += get_runtime_cmd_flags(&arg, (size_t)(p - arg));
+  assert(arg != NULL);  // suppress clang false positive
   source_runtime(arg, flags);
 }