Same problem for me with Ubuntu-Mate 18.04.1 32-bit. After a software update, the Software Boutique hangs. From the command-line, I get the error below when it hangs:
1 0xb370d464 /usr/lib/i386-linux-gnu/libjavascriptcoregtk-4.0.so.18(WTFCrash+0x14) [0xb370d464]
2 0xb331fcc9 /usr/lib/i386-linux-gnu/libjavascriptcoregtk-4.0.so.18(_ZN3JSC24ScratchRegisterAllocator15allocateScratchINS_7GPRInfoEEENT_12RegisterTypeEv+0xf9) [0xb331fcc9]
3 0xb3317318 /usr/lib/i386-linux-gnu/libjavascriptcoregtk-4.0.so.18(_ZN3JSC24ScratchRegisterAllocator18allocateScratchGPREv+0x18) [0xb3317318]
4 0xb2ee7284 /usr/lib/i386-linux-gnu/libjavascriptcoregtk-4.0.so.18(_ZN3JSC22GetterSetterAccessCase16emitDOMJITGetterERNS_21AccessGenerationStateEPKNS_6DOMJIT12GetterSetterENS_12X86Registers10RegisterIDE+0x354) [0xb2ee7284]
5 0xb2ea4d2e /usr/lib/i386-linux-gnu/libjavascriptcoregtk-4.0.so.18(_ZN3JSC10AccessCase12generateImplERNS_21AccessGenerationStateE+0x1dee) [0xb2ea4d2e]
6 0xb2ea50b6 /usr/lib/i386-linux-gnu/libjavascriptcoregtk-4.0.so.18(_ZN3JSC10AccessCase17generateWithGuardERNS_21AccessGenerationStateERNS_22AbstractMacroAssemblerINS_12X86AssemblerEE8JumpListE+0x146) [0xb2ea50b6]
7 0xb2efc0a3 /usr/lib/i386-linux-gnu/libjavascriptcoregtk-4.0.so.18(_ZN3JSC17PolymorphicAccess10regenerateERKNS_24GCSafeConcurrentJSLockerERNS_2VMEPNS_9CodeBlockERNS_17StructureStubInfoERKNS_10IdentifierE+0xc03) [0xb2efc0a3]
8 0xb2f0ddff /usr/lib/i386-linux-gnu/libjavascriptcoregtk-4.0.so.18(_ZN3JSC17StructureStubInfo13addAccessCaseERKNS_24GCSafeConcurrentJSLockerEPNS_9CodeBlockERKNS_10IdentifierESt10unique_ptrINS_10AccessCaseESt14default_deleteISA_EE+0x5af) [0xb2f0ddff]
9 0xb33162de /usr/lib/i386-linux-gnu/libjavascriptcoregtk-4.0.so.18(+0x7362de) [0xb33162de]
10 0xb33172a7 /usr/lib/i386-linux-gnu/libjavascriptcoregtk-4.0.so.18(_ZN3JSC14repatchGetByIDEPNS_9ExecStateENS_7JSValueERKNS_10IdentifierERKNS_12PropertySlotERNS_17StructureStubInfoENS_11GetByIDKindE+0x37) [0xb33172a7]
11 0xb32e7767 /usr/lib/i386-linux-gnu/libjavascriptcoregtk-4.0.so.18(+0x707767) [0xb32e7767]
12 0xaa7b942e [0xaa7b942e]
13 0xaa749e18 [0xaa749e18]
14 0xaa79bb98 [0xaa79bb98]
15 0xaa798cd8 [0xaa798cd8]
16 0xb3325cc6 /usr/lib/i386-linux-gnu/libjavascriptcoregtk-4.0.so.18(+0x745cc6) [0xb3325cc6]
17 0xb3320788 /usr/lib/i386-linux-gnu/libjavascriptcoregtk-4.0.so.18(+0x740788) [0xb3320788]
18 0xb32a0a3e /usr/lib/i386-linux-gnu/libjavascriptcoregtk-4.0.so.18(_ZN3JSC11Interpreter14executeProgramERKNS_10SourceCodeEPNS_9ExecStateEPNS_8JSObjectE+0xbbe) [0xb32a0a3e]