fix: ignore php composer lockfiles that are invalid (#5012)

Fixed issue where invalid lockfiles and metadata files were causing snyk container test to fail completely.
This change skips over invalid files.

Author: SteveShani

package-lock.json

@@ -114,7 +114,7 @@
     "semver": "^6.0.0",
     "snyk-config": "^5.0.0",
     "snyk-cpp-plugin": "2.24.0",
-    "snyk-docker-plugin": "^6.8.0",
+    "snyk-docker-plugin": "^6.8.3",
     "snyk-go-plugin": "1.23.0",
     "snyk-gradle-plugin": "4.0.2",
     "snyk-module": "3.1.0",