basic/string-table: reduce variable scope

src/basic/string-table.c

@@ -4,12 +4,10 @@
 #include "string-util.h"
 
 ssize_t string_table_lookup(const char * const *table, size_t len, const char *key) {
-        size_t i;
-
         if (!key)
                 return -1;
 
-        for (i = 0; i < len; ++i)
+        for (size_t i = 0; i < len; ++i)
                 if (streq_ptr(table[i], key))
                         return (ssize_t) i;