SCSS filter: blur cannot be compiled

Hi,

this looks like a bug for me. I cannot compile my fresh new created vaadin application
with this scss filter:

@mixin mytheme {
  @include valo;
	.test
	{
		filter: blur(5px);
	}
}

• Vaadin version: 8.1.5
• Eclipse: Oxygen
• Eclipse Vaadin Plugin (latest)
• OS: Linux

Steps to reproduce:
Create new Vaadin project, add this to theme and compile.

ERROR log:

[INFO] --- vaadin-maven-plugin:8.1.5:compile-theme (default-cli) @ myapplication ---
[INFO] Updating theme VAADIN/themes/mytheme
[ERROR] Okt 07, 2017 4:57:51 PM com.vaadin.sass.internal.handler.SCSSErrorHandler log
[ERROR] SCHWERWIEGEND: Error when parsing file 
[ERROR] /home/max/workspace/myapplication/src/main/webapp/VAADIN/themes/mytheme/mytheme.scss on line 39, column 25
[ERROR] Okt 07, 2017 4:57:51 PM com.vaadin.sass.internal.handler.SCSSErrorHandler log
[ERROR] SCHWERWIEGEND: encountered "5px". Was expecting one of: "=" "," ";" "." ")" "and" "or" "not" ":" "#{" "to" "through" "in" "from" <STRING> <NUMBER> <IDENT> <NOT_FUNCTION> <FUNCTION> 
[ERROR] org.w3c.css.sac.CSSParseException: encountered "5px". Was expecting one of: "=" "," ";" "." ")" "and" "or" "not" ":" "#{" "to" "through" "in" "from" <STRING> <NUMBER> <IDENT> <NOT_FUNCTION> <FUNCTION> 
[ERROR] 	at com.vaadin.sass.internal.parser.Parser.reportError(Parser.java:418)
[ERROR] 	at com.vaadin.sass.internal.parser.Parser.styleRule(Parser.java:2203)
[ERROR] 	at com.vaadin.sass.internal.parser.Parser.styleRuleOrDeclarationOrNestedProperties(Parser.java:5377)
[ERROR] 	at com.vaadin.sass.internal.parser.Parser.ifContentStatement(Parser.java:2990)
[ERROR] 	at com.vaadin.sass.internal.parser.Parser.mixinDirective(Parser.java:3620)
[ERROR] 	at com.vaadin.sass.internal.parser.Parser.topLevelDeclaration(Parser.java:559)
[ERROR] 	at com.vaadin.sass.internal.parser.Parser.parserUnit(Parser.java:487)
[ERROR] 	at com.vaadin.sass.internal.parser.Parser.parseStyleSheet(Parser.java:122)
[ERROR] 	at com.vaadin.sass.internal.ScssStylesheet.get(ScssStylesheet.java:172)
[ERROR] 	at com.vaadin.sass.internal.visitor.ImportNodeHandler.traverse(ImportNodeHandler.java:68)
[ERROR] 	at com.vaadin.sass.internal.tree.ImportNode.traverse(ImportNode.java:99)
[ERROR] 	at com.vaadin.sass.internal.tree.Node.traverseChildren(Node.java:227)
[ERROR] 	at com.vaadin.sass.internal.tree.Node.traverseChildren(Node.java:214)
[ERROR] 	at com.vaadin.sass.internal.ScssStylesheet.traverse(ScssStylesheet.java:298)
[ERROR] 	at com.vaadin.sass.internal.ScssStylesheet.compile(ScssStylesheet.java:267)
[ERROR] 	at com.vaadin.sass.SassCompiler.main(SassCompiler.java:101)
[ERROR] 
[ERROR] Okt 07, 2017 4:57:51 PM com.vaadin.sass.internal.handler.SCSSErrorHandler warn
[ERROR] WARNUNG: Warning when parsing file 
[ERROR] /home/max/workspace/myapplication/src/main/webapp/VAADIN/themes/mytheme/mytheme.scss on line 40, column 10
[ERROR] Okt 07, 2017 4:57:51 PM com.vaadin.sass.internal.handler.SCSSErrorHandler warn
[ERROR] WARNUNG: Skipping: }
[ERROR] org.w3c.css.sac.CSSParseException: Skipping: }
[ERROR] 	at com.vaadin.sass.internal.parser.Parser.reportWarningSkipText(Parser.java:434)
[ERROR] 	at com.vaadin.sass.internal.parser.Parser.topLevelDeclaration(Parser.java:618)
[ERROR] 	at com.vaadin.sass.internal.parser.Parser.parserUnit(Parser.java:487)
[ERROR] 	at com.vaadin.sass.internal.parser.Parser.parseStyleSheet(Parser.java:122)
[ERROR] 	at com.vaadin.sass.internal.ScssStylesheet.get(ScssStylesheet.java:172)
[ERROR] 	at com.vaadin.sass.internal.visitor.ImportNodeHandler.traverse(ImportNodeHandler.java:68)
[ERROR] 	at com.vaadin.sass.internal.tree.ImportNode.traverse(ImportNode.java:99)
[ERROR] 	at com.vaadin.sass.internal.tree.Node.traverseChildren(Node.java:227)
[ERROR] 	at com.vaadin.sass.internal.tree.Node.traverseChildren(Node.java:214)
[ERROR] 	at com.vaadin.sass.internal.ScssStylesheet.traverse(ScssStylesheet.java:298)
[ERROR] 	at com.vaadin.sass.internal.ScssStylesheet.compile(ScssStylesheet.java:267)
[ERROR] 	at com.vaadin.sass.SassCompiler.main(SassCompiler.java:101)
[ERROR] 
[ERROR] Compiling theme "VAADIN/themes/mytheme" failed
org.codehaus.mojo.gwt.shell.JavaCommandException: Command [[
/bin/sh -c '/usr/lib/jvm/java-8-oracle/jre/bin/java' '-Xmx1G' 'com.vaadin.sass.SassCompiler' '/home/max/workspace/myapplication/src/main/webapp/VAADIN/themes/mytheme/styles.scss' '/home/max/workspace/myapplication/src/main/webapp/VAADIN/themes/mytheme/styles.css'
]] failed with status 1
	at org.codehaus.mojo.gwt.shell.JavaCommand.execute(JavaCommand.java:330)
	at com.vaadin.integration.maven.CompileThemeMojo.processTheme(CompileThemeMojo.java:65)
	at com.vaadin.integration.maven.AbstractThemeMojo.doExecute(AbstractThemeMojo.java:43)
	at org.codehaus.mojo.gwt.shell.AbstractGwtShellMojo.execute(AbstractGwtShellMojo.java:182)
	at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:207)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
	at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
	at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193)
	at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106)
	at org.apache.maven.cli.MavenCli.execute(MavenCli.java:863)
	at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:288)
	at org.apache.maven.cli.MavenCli.main(MavenCli.java:199)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
	at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
	at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 3.486 s
[INFO] Finished at: 2017-10-07T16:57:52+02:00
[INFO] Final Memory: 16M/217M

Start with com.vaadin.sass.internal.parser.Parser.java, especially the styleRule parsing path named in the stack trace, and reproduce the failure with the Vaadin Maven compile-theme goal using the provided SCSS. Done means the sample theme containing filter: blur(5px) compiles successfully without the parser error.