Coverted error message to multiline string literal and used turnarty

operator on error message to ensure it isn't undefined.

index.js

@@ -58,14 +58,14 @@ async function main() {
             await cache.saveCache(cachePaths, cacheKey);
         } catch (e) {
             core.warning(
-                [
-                    "There was an error saving the pre-commit environments to cache:\n\n",
-                    `${e.message}\n\n`,
-                    "This only has performance implications and won't change the result of your pre-commit tests.\n",
-                    "If this problem persists on your default branch, you can try to fix it by editing your '.pre-commit-config.yaml'. ",
-                    "I.e. run 'pre-commit autoupdate' or simply add a blank line. ",
-                    "This will result in a different hash value and thus a different cache target.",
-                ].join("")
+                `There was an error saving the pre-commit environments to cache:
+
+                ${e.message ? e.message : e}
+
+                This only has performance implications and won't change the result of your pre-commit tests.
+                If this problem persists on your default branch, you can try to fix it by editing your '.pre-commit-config.yaml'.
+                I.e. run 'pre-commit autoupdate' or simply add a blank line.
+                This will result in a different hash value and thus a different cache target.`.replace(/  +/g, '')
             );
         }
     }