Regular expressions containing '+' are broken

[arjunaraoc]

Url is showing '+' with space and hence regexp containing '+' are failing to show results.

Example url:(which is broken as well as after regex_filter parameter 2 is appearing instead of &)
https://petscan.wmflabs.org/?&active_tab=tab_output&cb_labels_no_l=1&regexp_filter=^A.%20$2edits%5Bflagged%5D=both&edits%5Bbots%5D=both&sparql=SELECT%20?item%20?itemLabel%20WHERE%20{%0A%20%20?item%20wdt:P31%20wd:Q3624078.%0A%20%20SERVICE%20wikibase:label%20{%20bd:serviceParam%20wikibase:language%20%27en%27%20}%0A}&interface_language=en&common_wiki=wikidata&edits%5Banons%5D=both&since_rev0=&ns%5B0%5D=1&ores_prob_from=%C2%AEexp_filter&source_combination=sparql&project=wikipedia&language=en&cb_labels_yes_l=1&cb_labels_any_l=1&common_wiki_other=enwiki&search_max_results=500&

Regexp tried ^A.+$