Fix detection of negative integers when floating point is expected. (#…

…19821)

Our "see if it's an integer and append .0" code for floating point
only detected positive integers, so we were ending up with things like
"-1f" in generated code, which does not compile.

Fixes #19800

src/app/tests/suites/certification/Test_TC_MC_6_4.yaml

@@ -123,7 +123,6 @@ tests:
           value: 0
 
     - label: "Reads the PlaybackSpeed attribute from the DUT"
-      disabled: true
       command: "readAttribute"
       attribute: "PlaybackSpeed"
       response:
@@ -142,7 +141,6 @@ tests:
                 value: "Verify that the media play has reversed direction"
 
     - label: "Reads the PlaybackSpeed attribute from the DUT"
-      disabled: true
       command: "readAttribute"
       attribute: "PlaybackSpeed"
       response:

src/app/zap-templates/templates/app/helper.js

@@ -349,7 +349,7 @@ async function asTypedLiteral(value, type, cookie)
     // If the number looks like an integer, append ".0" to the end;
     // otherwise adding an "f" suffix makes compilers complain.
     value = value.toString();
-    if (value.match(/^[0-9]+$/)) {
+    if (value.match(/^-?[0-9]+$/)) {
       value = value + ".0";
     }
     return value + 'f';