Update benchmarks.yml

Author: jonathanmetzman

.github/workflows/benchmarks.yml

@@ -1,7 +1,7 @@
 name: Fuzzers+Benchmarks
 on:
   pull_request:
-    paths:
+    paths:d
       - 'docker/**'  # Base image changes.
       - 'fuzzers/**' # Changes to fuzzers themselves.
       - 'benchmarks/**'  # Changes to benchmarks.
@@ -58,7 +58,10 @@ jobs:
         sudo swapoff -a
         sudo rm -f /swapfile
         sudo apt clean
-        docker rmi $(docker images -a -q)
+        images=$(docker images -a -q)
+        if [ -n "$images" ]; then
+          docker rmi $images
+        fi
         df -h
 
     - name: Setup Python environment