fix: watch application, label selector is not used when name variable is not set

[xuhrc]

Fixes #5974 when name variable is empty, the label selector is not used.

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[codecov]

Codecov Report

Merging #5975 (a976b33) into master (1bc3348) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##           master    #5975   +/-   ##
=======================================
  Coverage   40.91%   40.91%           
=======================================
  Files         147      147           
  Lines       19635    19635           
=======================================
  Hits         8033     8033           
  Misses      10497    10497           
  Partials     1105     1105           

Impacted Files	Coverage Δ
server/application/application.go	30.55% <0.00%> (ø)

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[alexmt]

Nice catch @xuhrc ! Thank you!