tools/opt_common: Check for malloc failure

Fixes: CID1539100 Negative loop bound

Sponsored-by: Sovereign Tech Fund
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

fftools/opt_common.c

@@ -724,10 +724,13 @@ int show_codecs(void *optctx, const char *opt, const char *arg)
     return 0;
 }
 
-static void print_codecs(int encoder)
+static int print_codecs(int encoder)
 {
     const AVCodecDescriptor **codecs;
-    unsigned i, nb_codecs = get_codecs_sorted(&codecs);
+    int i, nb_codecs = get_codecs_sorted(&codecs);
+
+    if (nb_codecs < 0)
+        return nb_codecs;
 
     printf("%s:\n"
            " V..... = Video\n"
@@ -762,18 +765,17 @@ static void print_codecs(int encoder)
         }
     }
     av_free(codecs);
+    return 0;
 }
 
 int show_decoders(void *optctx, const char *opt, const char *arg)
 {
-    print_codecs(0);
-    return 0;
+    return print_codecs(0);
 }
 
 int show_encoders(void *optctx, const char *opt, const char *arg)
 {
-    print_codecs(1);
-    return 0;
+    return print_codecs(1);
 }
 
 int show_bsfs(void *optctx, const char *opt, const char *arg)