Fixed infinite loop when theming variable is missing

Author: samuelmaddock

lib/postcss-plugins.js

@@ -92,6 +92,7 @@ module.exports.replaceThemeVars = postcss.plugin('postcss-replace-theme-vars', (
                     decl.value = decl.value.replace(varRegex, varValue);
                 } else {
                     console.error(`Missing theming variable '${varName}'`);
+                    break;
                 }
             }
         });