Only add web client if a corresponding domain variable exists

src/freedombone-utils-android

                 "${app_name_upper}_DESCRIPTION"=
                 "${app_name_upper}_ICON_URL"=
                 "${app_name_upper}_MOBILE_APP_URL"=
-                if ! grep "${app_name_upper}_SHORT_DESCRIPTION=" "$app_filename"; then
+                if grep -q "${app_name_upper}_SHORT_DESCRIPTION=" "$app_filename"; then
                     # shellcheck disable=SC2140
                     "${app_name_upper}_SHORT_DESCRIPTION"="$(grep "${app_name_upper}_SHORT_DESCRIPTION=" "$app_filename" | head -n 1 | awk -F '=' '{print $2}')"
                 fi
-                if ! grep "${app_name_upper}_DESCRIPTION=" "$app_filename"; then
+                if grep -q "${app_name_upper}_DESCRIPTION=" "$app_filename"; then
                     # shellcheck disable=SC2140
                     "${app_name_upper}_DESCRIPTION"="$(grep "${app_name_upper}_DESCRIPTION=" "$app_filename" | head -n 1 | awk -F '=' '{print $2}')"
                 fi
-                if ! grep "${app_name_upper}_ICON_URL=" "$app_filename"; then
+                if grep -q "${app_name_upper}_ICON_URL=" "$app_filename"; then
                     # shellcheck disable=SC2140
                     "${app_name_upper}_ICON_URL"="$(grep "${app_name_upper}_ICON_URL=" "$app_filename" | head -n 1 | awk -F '=' '{print $2}')"
                 fi
-                if ! grep "${app_name_upper}_MOBILE_APP_URL=" "$app_filename"; then
+                if grep -q "${app_name_upper}_MOBILE_APP_URL=" "$app_filename"; then
                     # shellcheck disable=SC2140
                     "${app_name_upper}_MOBILE_APP_URL"="$(grep "${app_name_upper}_MOBILE_APP_URL=" "$app_filename" | head -n 1 | awk -F '=' '{print $2}')"
                 fi
 
                 { echo '    {';
                   echo "      \"name\": \"${app_name}\",";
-                  echo "      \"short_description\": \"${app_name_upper}_SHORT_DESCRIPTION\",";
-                  echo "      \"description\": \"${app_name_upper}_DESCRIPTION\",";
-                  echo "      \"icon_url\": \"${app_name_upper}_ICON_URL\",";
-                  echo "      \"clients\": [";
-                  echo '        {';
-                  echo "          \"name\": \"${app_name}\",";
-                  echo "          \"platforms\": [";
-                  echo '            {';
-                  echo '              "type": "web",';
-                  echo "              \"url\": \"${app_name_upper}_DOMAIN_NAME\"";
-                  echo '            }';
-                  echo '          ]';
-                  echo -n '        }'; } >> "$plinth_api"
+                  echo "      \"short_description\": \"$((${app_name_upper}_SHORT_DESCRIPTION))\",";
+                  echo "      \"description\": \"$((${app_name_upper}_DESCRIPTION))\",";
+                  echo "      \"icon_url\": \"$((${app_name_upper}_ICON_URL))\",";
+                  echo "      \"clients\": ["; } >> "$plinth_api"
 
-                if [[ $(("${app_name_upper}_MOBILE_APP_URL")) ]]; then
-                    { echo ',';
-                      echo '        {';
+                if [ $(("${app_name_upper}_DOMAIN_NAME")) ]; then
+                    { echo '        {';
+                      echo "          \"name\": \"${app_name}\",";
+                      echo "          \"platforms\": [";
+                      echo '            {';
+                      echo '              "type": "web",';
+                      echo "              \"url\": \"$((${app_name_upper}_DOMAIN_NAME))\"";
+                      echo '            }';
+                      echo '          ]';
+                      echo -n '        }'; } >> "$plinth_api"
+                fi
+
+                if [ $(("${app_name_upper}_MOBILE_APP_URL")) ]; then
+                    if [ $(("${app_name_upper}_DOMAIN_NAME")) ]; then
+                        echo ',' >> "$plinth_api"
+                    fi
+                    { echo '        {';
                       echo "          \"name\": \"${app_name}\",";
                       echo "          \"platforms\": [";
                       echo '            {';
                       echo '              "type": "store",';
                       echo '              "os": "android",';
                       echo '              "store_name": "f-droid",';
-                      echo "              \"url\": \"${app_name_upper}_MOBILE_APP_URL\"";
+                      echo "              \"url\": \"$((${app_name_upper}_MOBILE_APP_URL))\"";
                       echo '            }';
                       echo '          ]';
                       echo -n '        }'; } >> "$plinth_api"