decklink: fix FourCC opts without val

fixes the regression by commit d71c28e (2024-11-18)

Author: MartinPulec

src/video_capture/decklink.cpp

@@ -791,9 +791,13 @@ static bool parse_option(struct vidcap_decklink_state *s, const char *opt)
         } else if (strstr(opt, "keep-settings") == opt) {
                 s->keep_device_defaults = true;
         } else if ((strchr(opt, '=') != nullptr && strchr(opt, '=') - opt == 4) || strlen(opt) == 4) {
-                char val[STR_LEN];
-                snprintf_ch(val, "%s", strchr(opt, '=') + 1);
-                replace_all(val, DELDEL, ":");
+                char *val = nullptr;
+                char tmp[STR_LEN];
+                if (strchr(opt, '=') != nullptr) {
+                        snprintf_ch(tmp, "%s", strchr(opt, '=') + 1);
+                        replace_all(tmp, DELDEL, ":");
+                        val = tmp;
+                }
                 ret = s
                           ->device_options[(
                               BMDDeckLinkConfigurationID) bmd_read_fourcc(opt)]

src/video_display/decklink.cpp

@@ -1328,9 +1328,13 @@ static bool settings_init(struct state_decklink *s, const char *fmt,
                 } else if (strncasecmp(ptr, "targetbuffer=", strlen("targetbuffer=")) == 0) {
                         s->audio_drift_fixer.set_target_buffer(parse_uint32(strchr(ptr, '=') + 1));
                 } else if ((strchr(ptr, '=') != nullptr && strchr(ptr, '=') - ptr == 4) || strlen(ptr) == 4) {
-                        char val[STR_LEN];
-                        snprintf_ch(val, "%s", strchr(ptr, '=') + 1);
-                        replace_all(val, DELDEL, ":");
+                        char *val = nullptr;
+                        char tmp[STR_LEN];
+                        if (strchr(ptr, '=') != nullptr) {
+                                snprintf_ch(tmp, "%s", strchr(ptr, '=') + 1);
+                                replace_all(tmp, DELDEL, ":");
+                                val = tmp;
+                        }
                         ret &= s->device_options[(BMDDeckLinkConfigurationID)
                                                      bmd_read_fourcc(ptr)]
                                    .parse(val);