Fix potential NPE on exception path

[JENKINS-19082] Fix ListView includeRegex

Merge branch 'jenkins_19156_windows_processkiller' of https://github.com/synopsys-arc-oss/jenkins into pr903

Resolves https://issues.jenkins-ci.org/browse/JENKINS-19156Signed-off-by: NOleg Nenashev <nenashev@synopsys.com>

Conflicts:
	changelog.html

correct help text of Label field => can be a Label Expression

https://jenkins.ci.cloudbees.com/job/core/job/jenkins_main_trunk/1065/testReport/junit/hudson.model/ProjectTest/testPoll/

Eliminated the wrong script tag generation from <st:bind/>

(04:07:53 PM) bbeck: In a plugin, given hudson.model.Node object is there an easy way to figure out how many busy/idle executors that node has?  There only seems to be a method to determine the number of executors, but not their states.
(04:24:02 PM) kohsuke: bbeck: see Computer
(04:25:51 PM) bbeck: kohsuke: thanks, just noticed the countIdle/countBusy functions there.

Added another attribute 'checkDependsOn' on <input> elements (akin to
'fillDependsOn', etc) to list up the other dependency controls, and
insert appropriate onchange events.

'checkUrl' is now just the stem portion of the URL to invoke, and
the client script builds up the query parameters.

Findbug reported NP_NULL_ON_SOME_PATH_EXCEPTION, Priority: Normal

[FIXED JENKINS-9913] At least print a diagnostic to the build log if we are waiting on a checkpoint.

BuildStepCompatibilityLayer already implements BuildStep, so its subclasses need not say they do as well.

Also [JENKINS-19042] does not seem to have made it into 1.526; seems to have been towards 1.527.