Fix possible array index overflow in loader.c: fill_rsp()

Signed-off-by: INFINEON\DovhalA <Artem.Dovhal@infineon.com>
diff --git a/boot/bootutil/src/loader.c b/boot/bootutil/src/loader.c
index 645a789..b49de92 100644
--- a/boot/bootutil/src/loader.c
+++ b/boot/bootutil/src/loader.c
@@ -182,6 +182,10 @@
             break;
         }
     }
+    /* At least one image must be active, otherwise skip the execution */
+    if (BOOT_CURR_IMG(state) >= BOOT_IMAGE_NUMBER) {
+        return;
+    }
 #endif
 
 #if defined(MCUBOOT_DIRECT_XIP) || defined(MCUBOOT_RAM_LOAD)