Fix static analysis failures

src/freedombone-app-privatebin

           echo '  location / {'; } >> "$privatebin_nginx_site"
         function_check nginx_limits
         nginx_limits "$PRIVATEBIN_DOMAIN_NAME" '15m'
-        { echo '    try_files $uri $uri/ @privatebin;';
+        { echo "    try_files \$uri \$uri/ @privatebin;";
           echo '  }';
           echo '';
           echo '  # Restrict access that is unnecessary anyway';
       echo '  location / {'; } >> "$privatebin_nginx_site"
     function_check nginx_limits
     nginx_limits "$PRIVATEBIN_DOMAIN_NAME" '15m'
-    { echo '    try_files $uri $uri/ @privatebin;';
+    { echo "    try_files \$uri \$uri/ @privatebin;";
       echo '  }';
       echo '';
       echo '  # Restrict access that is unnecessary anyway';