fix: Fix issues with path handling in grep command Update is_contract.sh (#2359)

Author: ursulabauer

scripts/is_contract.sh

@@ -34,7 +34,14 @@ SOURCE_PATH=$(cargo metadata --format-version=1 --manifest-path "$MANIFEST_PATH"
     | select(.id == $ROOT_PACKAGE).targets[]
     | select(.kind[] | contains("lib")).src_path')
 
-if grep -q '^#\[ink::contract\([^]]*\)\]' $SOURCE_PATH; then
+# Check if SOURCE_PATH is empty
+if [ -z "$SOURCE_PATH" ]; then
+  echo "Error: Source path is empty."
+  exit 1
+fi
+
+# Check for the #[ink::contract] macro in the source file
+if grep -q '^#\[ink::contract\([^]]*\)\]' "$SOURCE_PATH"; then
     exit 0
 else
     exit 1