Fixes potential NPE when custom converters receive empty parameters #43709

Job	Run time
CI Sanity Check	31s
Attach pull request number	2s
Initial JDK 17 Build	12m 43s
Calculate Test Jobs	15s
Maven Tests - JDK 17	7m 45s
Maven Tests - JDK 17 Windows	12m 24s
Gradle Tests - JDK 17	27m 34s
Kubernetes Tests - JDK 17	11m 49s
Gradle Tests - JDK 17 Windows	56m 4s
JVM Tests - JDK 17	2h 45m 31s
Kubernetes Tests - JDK 21	10m 51s
JVM Tests - JDK 21	2h 48m 14s
Kubernetes Tests - JDK 17 Windows	17m 13s
JVM Tests - JDK 17 Windows	2h 49m 46s
Devtools Tests - JDK ${{ matrix.java.name }}	0s
Quickstarts Compilation - JDK 17	6m 38s
MicroProfile TCKs Tests	13m 24s
Native Tests - Main	1m 49s
Native Tests - Data1	30m 31s
Native Tests - Virtual Thread - Main	23m 35s
Native Tests - Data2	28m 50s
Native Tests - Virtual Thread - Messaging	10m 4s
Native Tests - Data3	20m 50s
Native Tests - Virtual Thread - Security	3m 37s
Native Tests - Data4	20m 0s
Native Tests - Data5	16m 30s
Native Tests - Data6	19m 34s
Native Tests - Data7	24m 28s
Native Tests - Amazon	15m 37s
Native Tests - Messaging1	24m 37s
Native Tests - Security2	16m 2s
Native Tests - Security3	8m 48s
Native Tests - Cache	14m 57s
Native Tests - HTTP	30m 1s
Native Tests - Misc1	10m 20s
Native Tests - Misc2	9m 36s
Native Tests - Misc3	21m 56s
Native Tests - Misc4	36m 58s
Native Tests - Spring	11m 47s
Native Tests - gRPC	15m 16s
Native Tests - Windows support	6m 40s
Upload build stats to collector	0s
Build report	40s
	18h 23m 47s

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