inp_fix_ternary_operator_str, limit backward search

src/frontend/inpcom.c

@@ -1917,7 +1917,7 @@ inp_fix_ternary_operator_str(char *line, bool all)
         fprintf(stderr, "ERROR: problem parsing ternary string %s!\n", line);
         controlled_exit(EXIT_FAILURE);
     }
-    str_ptr2 = skip_back_ws(colon);
+    str_ptr2 = skip_back_ws_(colon, str_ptr);
     keep = *str_ptr2;
     *str_ptr2 = '\0';
     if_str = inp_fix_ternary_operator_str(strdup(str_ptr), all);